Add new developer skills, auto-install git hooks, and Stripe MCP server (#889)

### Summary & Motivation

Expand the developer-cli with auto-installed git hooks, five new
agent-driven skills, and a Stripe MCP server for local development.

- **Auto-install git hooks via the developer-cli `install` command**: A
new `GitHooksSync` keeps `.git/hooks/` in sync with
`developer-cli/git-hooks/`, so any committed hook activates
automatically on `install` (and is removed on `uninstall`). Adds a
`pre-push` hook that rejects branch names which don't follow the
lowercase-kebab-case convention - GitHub's server-side branch-name
restriction is Enterprise-only, so client-side enforcement closes the
gap. Replaces the manual `core.hooksPath` wiring previously done by the
`mcp-setup` command.
- **Five new skills**:
  - `commit` — converts the commit slash-command into a skill.
  - `db-query` — psql access to the local Aspire Postgres.
- `rebuild-branch` — cherry-picks each commit of a stale branch onto a
fresh one off main with per-commit validation.
- `pull-platformplatform-changes` — cherry-picks unmerged upstream PRs
into a downstream project.
- A new skill for opening GitHub PRs end-to-end, replacing the older
description-only command of the same purpose.
- **Stripe MCP server**: `.claude/scripts/stripe-mcp-dev.sh` reads the
dev sandbox key from `dotnet user-secrets` and execs `@stripe/mcp`.
Wired into `.mcp.json` for local agent use.

### Checklist

- [x] I have added tests, or done manual regression tests
- [x] I have updated the documentation, if necessary

Author: tjementum

.claude/commands/commit.md

@@ -0,0 +1,17 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Reads the Stripe dev sandbox key from dotnet user-secrets and execs @stripe/mcp.
+# Today this uses sk_test_* (full perms, test-mode only). Swap to a read-only
+# rk_test_* restricted key by changing the secret name below.
+SECRET_NAME="Parameters:stripe-api-key"
+
+STRIPE_SECRET_KEY=$(dotnet user-secrets list --project application/AppHost/AppHost.csproj | sed -n "s/^${SECRET_NAME} = //p")
+
+if [ -z "$STRIPE_SECRET_KEY" ]; then
+  echo "Stripe MCP: secret '${SECRET_NAME}' not found in dotnet user-secrets." >&2
+  exit 1
+fi
+
+export STRIPE_SECRET_KEY
+exec npx -y @stripe/mcp

.claude/commands/prepare-pull-request.md

@@ -0,0 +1,60 @@
+---
+name: commit
+description: Commit session changes to git. Identify files from session context, ask user pick message, run validation only if needed. Use when user want commit / save / land changes.
+allowed-tools: *
+---
+
+# Commit Workflow
+
+**Asked commit now != permission for future commits.** Each commit needs explicit user instruction. No amend, revert, push without explicit ask.
+
+Speed critical. No slow commands unless changes warrant.
+
+## Identify Files
+
+- Prefer session context over re-running `git status` / `log` / `diff`.
+- Clean session: all changed files. With context: only files you changed.
+
+## Translations
+
+Frontend changes touching user-facing strings: run `translate` to check `.po` files. Missing keys: flag user; don't commit until resolved.
+
+## Validation (judgment)
+
+Skip if `build` / `test` / `lint` / `format` / `aspire-restart` / `e2e` already ran clean this session on same files. No re-run, no offer.
+
+When need:
+
+Run `build` first:
+- **Backend change:** `build` (no flags - covers backend AND frontend; backend can break frontend via API contracts)
+- **Frontend-only:** `build --frontend`
+- **CLI-only:** `build --cli`
+
+After build, parallel (`--no-build` where applicable):
+
+- `format --<target>`, `lint --<target>` - per target whose code changed
+- `test --no-build` - backend change
+- `aspire-restart` - service / Aspire wiring change (large only)
+- `e2e` - large frontend or shared E2E-covered change; `--smoke` for low-impact (rare pre-commit)
+
+Judge target by file (project / manifest / lock files affect owning build, even when extension non-obvious).
+
+## Ask User
+
+Simple, focused commit: propose one message, commit.
+
+Complex (multiple unrelated changes, doesn't fit one line, validation choices needed, file set ambiguous): use AskUserQuestion - 2-4 message options + conditionals in one call. No back-and-forth. Follow up only on "Other" or unexpected input.
+
+No conventional commit prefixes (`feat:`, `fix:`, `docs:`, `chore:`).
+
+Conditional questions:
+- Validation tools multi-select, only those flagged needed. Default skip.
+- File selection if ambiguous.
+
+## Stage and Commit
+
+Stage explicit files. Never `git add -A` or `git add .`.
+
+---
+
+Asked commit now != permission for future commits.