Add knip config for dead code detection

Configure knip with workspace awareness for the TKO monorepo.
Add `bun run knip` script. Remove unused fs-extra devDependency.

Findings (config only, no code changes):
- 3 unused files, 8 unused deps, 10 unlisted deps
- 10 unused exports, 19 unused exported types, 2 duplicate exports
These will be addressed in Phase 6 (separate PRs per category).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: 2 people

AGENTS.md

@@ -43,6 +43,7 @@ bun run lint              # Run Biome lint only
 bun run lint:fix          # Run Biome lint with auto-fix
 bun run format            # Check Biome formatting
 bun run format:fix        # Fix Biome formatting
+bun run knip              # Detect unused files, deps, and exports
 bun run tsc               # TypeScript type-check (no emit)
 bun run dts               # Generate TypeScript declaration files
 bun run clean             # Clean dist/ and coverage/ dirs

bun.lock

@@ -0,0 +1,24 @@
+{
+  "$schema": "https://unpkg.com/knip@5/schema.json",
+  "workspaces": {
+    ".": {
+      "entry": ["vitest.config.ts", "tools/build.ts"],
+      "project": ["*.ts", "tools/**/*.ts"]
+    },
+    "packages/*": {
+      "entry": ["index.ts", "src/index.ts"],
+      "project": ["src/**/*.ts"]
+    },
+    "builds/*": {
+      "entry": ["index.ts", "src/index.ts"],
+      "project": ["src/**/*.ts"]
+    }
+  },
+  "ignoreDependencies": [
+    "tslib",
+    "@vitest/browser",
+    "@vitest/browser-playwright",
+    "esbuild",
+    "playwright"
+  ]
+}

knip.json

@@ -17,6 +17,7 @@
     "lint": "bunx @biomejs/biome lint .",
     "lint:fix": "bunx @biomejs/biome check --fix .",
     "check": "bunx @biomejs/biome check .",
+    "knip": "bunx knip",
     "verify:esm": "bun tools/verify-esm-extensions.ts",
     "verify": "bunx @biomejs/biome check . && bunx tsc && bun run build && bun run verify:esm && bunx vitest run",
     "clean": "rm -rf packages/*/dist builds/*/dist coverage"
@@ -37,7 +38,6 @@
     "@vitest/browser-playwright": "^4.1.4",
     "chai": "^6.2.2",
     "esbuild": "^0.28.0",
-    "fs-extra": "^11.3.2",
     "jquery": "^4.0.0",
     "playwright": "^1.59.1",
     "sinon": "^21.0.3",

package.json

@@ -0,0 +1,45 @@
+# Plan: Add knip for dead code detection
+
+## Context
+
+knip detects unused files, dependencies, exports, and types in the codebase.
+A previous attempt (PR #234) was reverted because it mixed the linter setup
+with code changes (verbatimModuleSyntax, type refactoring, export cleanup)
+in a single 56-file PR.
+
+This time: Phase 5 adds the linter config + CI only. Phase 6 fixes findings
+in separate, focused PRs.
+
+## Findings (with config)
+
+| Category | Count | Notes |
+|---|---|---|
+| Unused files | 3 | `builds/*/src/common.ts`, `tools/template/index.ts` |
+| Unused dependencies | 8 | `@tko/*` packages not imported, declared in package.json |
+| Unused devDependencies | 1 | `fs-extra` (leftover from old tooling) |
+| Unlisted dependencies | 10 | `@tko/*` imports missing from package.json |
+| Unused exports | 10 | Functions/classes exported but never imported |
+| Unused exported types | 19 | Type-only exports never imported |
+| Duplicate exports | 2 | Same symbol exported under two names |
+
+## What this PR does
+
+1. Add `knip.json` config with workspace awareness
+2. Add `bun run knip` script to package.json
+3. Add knip to CI (warn-only, non-blocking initially)
+4. Remove `fs-extra` from devDependencies (genuinely unused)
+5. Update AGENTS.md and plans/
+
+## What this PR does NOT do
+
+- No source code changes (no removing exports, deps, or files)
+- No `verbatimModuleSyntax`
+- No type refactoring
+- Those come in Phase 6, one category per PR
+
+## Verification
+
+1. `bunx knip` runs cleanly with known findings
+2. `bun run build` still works
+3. `bunx vitest run` still passes
+4. CI workflow runs and reports findings