docs: enhance 5 thin commands and add Rust API example

Commands enhanced with multi-language support, error recovery strategies,
and structured step-by-step workflows:
- build-fix: build system detection table, fix loop, recovery strategies
- test-coverage: framework detection, test generation rules, before/after report
- refactor-clean: safety tiers (SAFE/CAUTION/DANGER), multi-language tools
- update-codemaps: codemap format spec, diff detection, metadata headers
- update-docs: source-of-truth mapping, staleness checks, generated markers

New example:
- rust-api-CLAUDE.md: Axum + SQLx + PostgreSQL with layered architecture,
  thiserror patterns, compile-time SQL verification, integration test examples

commands/refactor-clean.md

@@ -1,28 +1,80 @@
 # Refactor Clean
 
-Safely identify and remove dead code with test verification:
+Safely identify and remove dead code with test verification at every step.
 
-1. Run dead code analysis tools:
-   - knip: Find unused exports and files
-   - depcheck: Find unused dependencies
-   - ts-prune: Find unused TypeScript exports
+## Step 1: Detect Dead Code
 
-2. Generate comprehensive report in .reports/dead-code-analysis.md
+Run analysis tools based on project type:
 
-3. Categorize findings by severity:
-   - SAFE: Test files, unused utilities
-   - CAUTION: API routes, components
-   - DANGER: Config files, main entry points
+| Tool | What It Finds | Command |
+|------|--------------|---------|
+| knip | Unused exports, files, dependencies | `npx knip` |
+| depcheck | Unused npm dependencies | `npx depcheck` |
+| ts-prune | Unused TypeScript exports | `npx ts-prune` |
+| vulture | Unused Python code | `vulture src/` |
+| deadcode | Unused Go code | `deadcode ./...` |
+| cargo-udeps | Unused Rust dependencies | `cargo +nightly udeps` |
 
-4. Propose safe deletions only
+If no tool is available, use Grep to find exports with zero imports:
+```
+# Find exports, then check if they're imported anywhere
+```
 
-5. Before each deletion:
-   - Run full test suite
-   - Verify tests pass
-   - Apply change
-   - Re-run tests
-   - Rollback if tests fail
+## Step 2: Categorize Findings
 
-6. Show summary of cleaned items
+Sort findings into safety tiers:
 
-Never delete code without running tests first!
+| Tier | Examples | Action |
+|------|----------|--------|
+| **SAFE** | Unused utilities, test helpers, internal functions | Delete with confidence |
+| **CAUTION** | Components, API routes, middleware | Verify no dynamic imports or external consumers |
+| **DANGER** | Config files, entry points, type definitions | Investigate before touching |
+
+## Step 3: Safe Deletion Loop
+
+For each SAFE item:
+
+1. **Run full test suite** — Establish baseline (all green)
+2. **Delete the dead code** — Use Edit tool for surgical removal
+3. **Re-run test suite** — Verify nothing broke
+4. **If tests fail** — Immediately revert with `git checkout -- <file>` and skip this item
+5. **If tests pass** — Move to next item
+
+## Step 4: Handle CAUTION Items
+
+Before deleting CAUTION items:
+- Search for dynamic imports: `import()`, `require()`, `__import__`
+- Search for string references: route names, component names in configs
+- Check if exported from a public package API
+- Verify no external consumers (check dependents if published)
+
+## Step 5: Consolidate Duplicates
+
+After removing dead code, look for:
+- Near-duplicate functions (>80% similar) — merge into one
+- Redundant type definitions — consolidate
+- Wrapper functions that add no value — inline them
+- Re-exports that serve no purpose — remove indirection
+
+## Step 6: Summary
+
+Report results:
+
+```
+Dead Code Cleanup
+──────────────────────────────
+Deleted:   12 unused functions
+           3 unused files
+           5 unused dependencies
+Skipped:   2 items (tests failed)
+Saved:     ~450 lines removed
+──────────────────────────────
+All tests passing ✅
+```
+
+## Rules
+
+- **Never delete without running tests first**
+- **One deletion at a time** — Atomic changes make rollback easy
+- **Skip if uncertain** — Better to keep dead code than break production
+- **Don't refactor while cleaning** — Separate concerns (clean first, refactor later)