chore(ci): add lefthook git hooks manager

[iap]

Summary

Adds Lefthook for git hook management to the template.

• lefthook.yml — pre-commit (npm run lint) + commit-msg (type(scope): summary)
• .lefthook/commit-msg/commit-msg-lint.sh — validates commit message format
• README.md — documents setup via lefthook install

Verification

• lefthook validate passes
• Valid messages (feat:, fix(core):, docs:, chore(ci):) accepted
• Invalid messages ("add feature", "WIP", "fix bug") rejected
• Merge commits skipped

Setup

mise use lefthook   # or your package manager
lefthook install

Override with git commit --no-verify when needed.

Greptile Summary

Adds Lefthook-managed pre-commit linting and commit-message validation, with installation guidance in the README. The earlier report that lint failures could be suppressed is disproved: when a present project's lint script exited 23, the configured pre-commit command also exited 23 rather than allowing the commit to proceed.

Confidence Score: 5/5

No blocking failure remains.

The configured lint command propagates failures, and the commit-message validator correctly rejects invalid subjects while accepting documented conventional and merge subjects.

T-Rex Logs

What T-Rex did

• Ran the pre-commit hook harness against temporary projects and observed a lint failure (exit 23) and a subsequent lint success (exit 0).
• Validated the commit-message validator by testing a nonconforming subject which was rejected (exit 1) and by testing conventional and merge subjects which were accepted (exit 0 each).
• Parsed the Lefthook configuration and ran YAML and Bash syntax checks to confirm the declared hooks, runner, and script syntax are valid.

_{Ran code and verified through T-Rex}

_{Reviews (3): Last reviewed commit: "chore(ci): add lefthook git hooks manage..." | Re-trigger Greptile}