[CLAUDE ROUTINE]: Test-coverage enhancement — loader edge cases (symlinks, deep transitive imports, timeout cleanup) #157

Summary

The custom-hooks loader has well-covered happy paths but a few edge cases worth locking in with tests:

• Symlinks inside a policy's import tree
• Deep transitive imports (a.js → b.js → c.js)
• Temp-file cleanup when loadSingleFile throws mid-rewrite
• Name collisions between an explicit customPoliciesPath and a convention file
• Fail-open logging path (broken file → warning, no crash)

Where

• src/hooks/custom-hooks-loader.ts (205 lines)
• src/hooks/loader-utils.ts (178 lines)
• __tests__/hooks/custom-hooks-loader.integration.test.ts
• __tests__/hooks/loader-utils.test.ts

Why this helps

The loader is one of the most complex pieces of code in the tree and it runs on every hook. Each edge case above has burned someone once. Tests pin the current behaviour (even if nuanced) so future refactors — including several of the perf enhancements in this batch — don't regress them silently.

Proposed enhancement

Add these cases:

1. Symlinks in the import tree
   • Policy entry imports a file that's a symlink inside the same project — loader follows it once, no infinite loop.
2. Deep transitive imports
   • entry.js → a.js → b.js → c.js; assert every file is rewritten and the hooks from c.js register.
3. Cleanup on error
   • Entry imports a file with a syntax error. Loader should unlink every .__failproofai_tmp__.mjs it created, not just the entry.
4. Convention + explicit collision
   • A convention file and the explicit customPoliciesPath both register a hook named "my-hook". Assert the explicit one is NOT tagged with __conventionScope (current code handles this; lock it in).
5. Fail-open warning
   • Nonexistent customPoliciesPath + strict: false → hookLogWarn fires, returns empty list, no throw.

Acceptance criteria

• One test per case above, all passing.
• No flaky temp-file leakage between tests (each test cleans its own fixture dir in afterEach).
• rewriteFileTree coverage includes the symlink and deep-tree paths.