feat: add /add-feature command, feature manifest system, and scaffold-default.sh

- New /add-feature command (26th command, 10th starter-kit) for adding
  capabilities (MongoDB, Docker, testing, etc.) to existing projects
- Feature manifest system (.claude/features.json) tracks installed features
  per project for /update-project to sync source file changes
- Enhanced /update-project with Step 3b (feature file inventory) and
  Step 5d (feature file updates) to sync feature source files
- New scaffold-default.sh batch script for default profile (Next.js +
  MongoDB + Tailwind + Docker + SEO + CI) — creates 67 files in ~3s
- Updated new-project.md, convert-project-to-starter-kit.md, and
  scaffold-clean.sh to write feature manifests
- Doc sync: 25→26 commands, 9→10 starter-kit across all 5 locations

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: timclausendev-web

.claude/commands/add-feature.md

@@ -0,0 +1,354 @@
+---
+description: Add a capability (MongoDB, Docker, testing, etc.) to an existing project
+scope: starter-kit
+argument-hint: <feature> [--list | --force]
+allowed-tools: Read, Write, Edit, Bash, Grep, Glob, AskUserQuestion
+---
+
+# Add Feature to Existing Project
+
+Add capabilities (MongoDB, Docker, testing, etc.) to an existing starter-kit project after scaffolding. Idempotent — safely updates already-installed features to the latest version.
+
+**Arguments:** $ARGUMENTS
+
+---
+
+## Feature Definitions
+
+The authoritative table of features that can be added to projects. Both `/add-feature` and `/update-project` reference these definitions.
+
+| Feature | Files (from $SOURCE) | Deps | DevDeps | Env Vars | Scripts | CLAUDE.md Rule |
+|---------|---------------------|------|---------|----------|---------|----------------|
+| `mongo` | `src/core/db/index.ts`, `scripts/db-query.ts`, `scripts/queries/example-find-user.ts`, `scripts/queries/example-count-docs.ts` | `mongodb@^6.5.0` | `tsx@^4.7.0` | `MONGODB_URI`, `MONGO_DB_NAME`, `DB_SANITIZE_INPUTS` | `db:query`, `db:query:list` | Rule 3 |
+| `postgres` | `src/core/db/sql.ts` | `pg@^8.0.0` | — | `DATABASE_URL` | — | Rule 3b |
+| `docker` | Generated from templates (Dockerfile, docker-compose.yml) | — | — | — | — | Rule 10 |
+| `vitest` | `vitest.config.ts` | — | `vitest@^2.0.0` | — | `test:unit`, `test:unit:watch`, `test:coverage` | — |
+| `playwright` | `playwright.config.ts` | — | `@playwright/test@^1.42.0` | — | `test:e2e`, `test:e2e:ui`, `test:e2e:headed`, `test:e2e:chromium`, `test:e2e:report`, `test:kill-ports` | Rule 4 |
+| `content` | `scripts/build-content.ts`, `scripts/content.config.json` | — | — | — | `content:build`, `content:build:id`, `content:list` | — |
+
+---
+
+## Step 0 — Resolve Source (Starter Kit)
+
+Find the starter kit source directory:
+
+1. If CWD has BOTH `claude-mastery-project.conf` AND `.claude/commands/new-project.md` → use CWD as `$SOURCE`
+2. Else read `~/.claude/starter-kit-source-path` → verify it still has both files
+3. Else ask via AskUserQuestion: "Where is the starter kit cloned?" with a text input
+
+Store as `$SOURCE`.
+
+---
+
+## Step 1 — Parse Arguments
+
+Parse `$ARGUMENTS` for:
+
+- `--list` → display the Feature Definitions table above and exit immediately
+- `--force` → set `$FORCE=true` (skip confirmation prompts)
+- Everything else → feature name(s), space-separated (e.g., `mongo vitest`)
+
+**Validate feature names:** Each name must match one of the features in the table above. If unknown: "Unknown feature: `<name>`. Use `/add-feature --list` to see available features."
+
+If no feature names and no `--list`: ask via AskUserQuestion:
+"Which feature do you want to add?"
+- **mongo** — MongoDB wrapper, query system, connection pool management
+- **postgres** — SQL wrapper with parameterized queries, transaction support
+- **vitest** — Unit/integration test framework with coverage
+- **playwright** — E2E browser testing with multi-browser support
+
+(Show up to 4 most common; user can type "Other" for docker, content, etc.)
+
+---
+
+## Step 2 — Select Target
+
+1. Read `~/.claude/starter-kit-projects.json`
+   - If file doesn't exist or empty → error: "No projects found. Use `/new-project` to create one first."
+
+2. **Smart default:** If CWD is inside a registered project directory → offer it first
+
+3. Filter to projects whose `path` directory still exists on disk
+
+4. Display list with AskUserQuestion:
+   - "Which project should receive the feature?"
+   - Options: up to 4 most recent projects (by `createdAt`), each showing: `name — language/framework — path`
+   - If more than 4: the 4th option should be "Other (type a path)"
+
+5. Store selected path as `$TARGET`
+
+### Validations (all must pass — stop with clear error if any fail)
+
+1. `$TARGET` directory exists → if not: "Directory not found: $TARGET"
+2. `$TARGET` is a git repo → run: `git -C "$TARGET" rev-parse --is-inside-work-tree 2>/dev/null`
+   - If not a git repo: "This project must be a git repo."
+3. `$TARGET` is NOT the starter kit itself (compare resolved paths of `$SOURCE` and `$TARGET`)
+   - If same: "Cannot add features to the starter kit itself."
+4. `$TARGET` is registered in `~/.claude/starter-kit-projects.json`
+   - If not registered: "This project isn't in the registry. Use `/convert-project-to-starter-kit` first."
+
+---
+
+## Step 3 — Safety Commit
+
+```bash
+cd "$TARGET"
+git status --porcelain
+```
+
+- **If uncommitted changes exist** (git status --porcelain has output):
+  ```bash
+  cd "$TARGET" && git add -A && git commit -m "chore: pre-feature snapshot (before /add-feature)"
+  ```
+
+- **If clean** (no uncommitted changes):
+  ```bash
+  cd "$TARGET" && git commit --allow-empty -m "chore: pre-feature marker (before /add-feature)"
+  ```
+
+Store the hash: `PRE_FEATURE_HASH=$(git -C "$TARGET" rev-parse HEAD)`
+
+**STOP if git fails** (except "nothing to commit" which is fine — treat as clean).
+
+---
+
+## Step 4 — Read Manifest
+
+Read `$TARGET/.claude/features.json`.
+
+**If missing:** Create an empty manifest:
+
+```json
+{
+  "schemaVersion": 1,
+  "installedBy": "claude-code-mastery-starter-kit",
+  "language": "unknown",
+  "features": {}
+}
+```
+
+Write it to `$TARGET/.claude/features.json`.
+
+**If exists:** Parse it. For each requested feature, check if it's already installed:
+
+- **Already installed, same files:** Ask via AskUserQuestion (unless `$FORCE`):
+  "Feature `<name>` is already installed (since <installedAt>). Update to latest version?"
+  - Yes, update files (Recommended)
+  - No, skip this feature
+
+- **Not installed:** Proceed to install
+
+---
+
+## Step 5 — Preview (unless --force)
+
+For each feature to install/update, display:
+
+```
+=== Feature Preview: <name> ===
+
+Files to copy:
+  + src/core/db/index.ts
+  + scripts/db-query.ts
+  + scripts/queries/example-find-user.ts
+  + scripts/queries/example-count-docs.ts
+
+Dependencies to install:
+  mongodb@^6.5.0
+  tsx@^4.7.0 (dev)
+
+Environment variables to add (.env.example):
+  MONGODB_URI=your_mongodb_connection_string_here
+  MONGO_DB_NAME=your_database_name
+  DB_SANITIZE_INPUTS=true
+
+Scripts to add (package.json):
+  db:query → tsx scripts/db-query.ts
+  db:query:list → tsx scripts/db-query.ts --list
+
+CLAUDE.md sections:
+  Rule 3: Database Access — Wrapper Only (if missing)
+```
+
+Ask via AskUserQuestion:
+"Proceed with installing <N> feature(s)?"
+- **Yes, install** (Recommended)
+- **No, cancel**
+
+If "No, cancel" → stop: "Feature installation cancelled. No changes made."
+
+---
+
+## Step 6 — Execute
+
+For each feature, in order:
+
+### 6a. Create directories
+
+```bash
+mkdir -p "$TARGET/$(dirname <each-file>)"
+```
+
+### 6b. Copy files
+
+For each file in the feature definition:
+- Copy from `$SOURCE/<file>` → `$TARGET/<file>`
+- If file already exists and this is an update → overwrite
+
+### 6c. Install dependencies (Node.js projects only)
+
+Detect package manager from target project:
+- `pnpm-lock.yaml` exists → `pnpm`
+- `bun.lockb` exists → `bun`
+- Otherwise → `npm`
+
+```bash
+cd "$TARGET"
+# Production deps
+<pkg-manager> add <deps>
+# Dev deps
+<pkg-manager> add -D <devDeps>
+```
+
+Skip if no deps defined for the feature. Skip if deps already in package.json.
+
+### 6d. Merge .env.example
+
+For each env var in the feature definition:
+1. Read `$TARGET/.env.example` (create if missing)
+2. Check if key name (before `=`) already exists
+3. If missing → append the line with placeholder value
+4. Write back
+
+**Env var placeholder values:**
+- `MONGODB_URI` → `your_mongodb_connection_string_here`
+- `MONGO_DB_NAME` → `your_database_name`
+- `DB_SANITIZE_INPUTS` → `true`
+- `DATABASE_URL` → `your_database_url_here`
+
+### 6e. Merge package.json scripts
+
+For each script in the feature definition:
+1. Read `$TARGET/package.json` as JSON
+2. Check if script name already exists in `scripts`
+3. If missing → add it
+4. Write back (preserve formatting)
+
+**Script values:**
+- `db:query` → `tsx scripts/db-query.ts`
+- `db:query:list` → `tsx scripts/db-query.ts --list`
+- `test:unit` → `vitest run`
+- `test:unit:watch` → `vitest`
+- `test:coverage` → `vitest run --coverage`
+- `test:e2e` → `pnpm test:kill-ports && playwright test`
+- `test:e2e:ui` → `pnpm test:kill-ports && playwright test --ui`
+- `test:e2e:headed` → `pnpm test:kill-ports && playwright test --headed`
+- `test:e2e:chromium` → `pnpm test:kill-ports && playwright test --project=chromium`
+- `test:e2e:report` → `playwright show-report`
+- `test:kill-ports` → `lsof -ti:4000,4010,4020 | xargs kill -9 2>/dev/null || true`
+- `content:build` → `tsx scripts/build-content.ts`
+- `content:build:id` → `tsx scripts/build-content.ts --id`
+- `content:list` → `tsx scripts/build-content.ts --list`
+
+### 6f. Add CLAUDE.md sections (if missing)
+
+Check if the relevant CLAUDE.md rule section exists by searching for the header text. If missing, append it.
+
+**mongo → Rule 3 header check:** Search for `Database Access` or `Wrapper Only` in `$TARGET/CLAUDE.md`
+If missing, append the full Rule 3 section from the starter kit's CLAUDE.md.
+
+**postgres → Rule 3b header check:** Search for `SQL Database Access` in `$TARGET/CLAUDE.md`
+If missing, append the full Rule 3b section.
+
+**playwright → Rule 4 header check:** Search for `Testing — Explicit Success Criteria` in `$TARGET/CLAUDE.md`
+If missing, append the full Rule 4 section.
+
+### 6g. Special: Docker feature
+
+Docker doesn't copy files from source — it generates them based on the target project:
+
+1. Detect language from registry or `$TARGET/.claude/features.json`
+2. Generate `Dockerfile` using the appropriate template from the starter kit's `/new-project` command:
+   - Node.js → multi-stage with node:20-alpine
+   - Go → multi-stage with golang:1.23-alpine → scratch
+   - Python → multi-stage with python:3.12-slim
+3. Generate `.dockerignore` if missing
+4. Add docker-related scripts if applicable
+
+---
+
+## Step 7 — Update Manifest
+
+For each installed/updated feature, write to `$TARGET/.claude/features.json`:
+
+```json
+{
+  "schemaVersion": 1,
+  "installedBy": "claude-code-mastery-starter-kit",
+  "language": "<from-registry-or-detection>",
+  "features": {
+    "<feature-name>": {
+      "version": "1.0.0",
+      "installedAt": "<ISO-timestamp>",
+      "updatedAt": "<ISO-timestamp-or-null>",
+      "files": [
+        "<list-of-files-copied>"
+      ]
+    }
+  }
+}
+```
+
+- New install: set `installedAt` to now, `updatedAt` to null
+- Update: keep original `installedAt`, set `updatedAt` to now
+
+---
+
+## Step 8 — Commit + Summary
+
+```bash
+cd "$TARGET"
+git add -A
+git commit -m "feat: add <feature-name(s)> via /add-feature"
+```
+
+Store: `FEATURE_HASH=$(git -C "$TARGET" rev-parse HEAD)`
+
+**If nothing to commit** (all files unchanged): skip the commit, note "Already up to date."
+
+### Display summary
+
+```
+=== Feature Installation Complete ===
+
+Target: $TARGET
+Feature(s): <name(s)>
+
+Files:        N added, N updated
+Dependencies: N installed
+Env vars:     N added to .env.example
+Scripts:      N added to package.json
+CLAUDE.md:    N sections added
+
+Pre-feature commit:  $PRE_FEATURE_HASH
+Feature commit:      $FEATURE_HASH
+
+To undo: git revert HEAD
+To review: git diff $PRE_FEATURE_HASH..HEAD
+
+Manifest updated: .claude/features.json
+```
+
+---
+
+## Edge Cases
+
+1. **Feature already installed and up to date** — If all files are identical to source, report "Feature `<name>` is already up to date — no changes needed." and skip.
+
+2. **No package.json** — If the target has no package.json (e.g., Go or Python project), skip dependency installation and script merging. Still copy files and update manifest.
+
+3. **Multiple features at once** — Process each feature sequentially. One commit at the end with all features listed.
+
+4. **Go/Python projects requesting mongo** — Copy the Node.js wrapper files but skip npm dependency installation. Note in summary: "Files copied but dependencies not installed (not a Node.js project). Install the MongoDB driver for your language manually."
+
+5. **Source file missing** — If a file listed in the feature definition doesn't exist in `$SOURCE`, warn and skip that file. Don't fail the entire operation.