fix: handle empty staged files in pre-commit hook

[jmcte]

Summary

• Make the generated pre-commit hook safe when its staged-file list is empty under Bash set -u.
• Add a smoke test that invokes the generated hook from a clean feature branch.

Governing Issue

Closes #109.

Validation

• TMPDIR=/tmp npm run check (23 test files, 194 tests passed)
• npm run build
• bash scripts/ci/check-action-pins.sh (42 pins passed)
• git diff --check origin/main...HEAD
• Original exact-head autoreview reported no accepted/actionable findings; rebased patch retains stable patch-id e3edfd4aeee202498289c2bebca2054ac119432c.
• Required PR checks are expected to satisfy CI Gate.

Bootstrap Governance

• Changes remain scoped to Bootstrap's generated hook and its regression coverage.
• Contributor guidance and managed-repository policy are unchanged.
• No secrets, credentials, or machine-local state are introduced.
• The placeholder commit identity was replaced with the repository maintainer's verified GitHub no-reply identity during rebase.

Material change: no

Merge Automation

• Auto-merge is armed with squash merge for the current head.

Notes

Current head: 9ae56f973d32c49cf12f4f51c48c176fe039a678.

The previous head 0addaae10a44cce10fff99651631a882b774cf7f and rebased head carry the same stable patch-id. The rebase changes only ancestry and commit identity; behavior remains the previously reviewed two-file fix.

[athena-omt]

Reviewed current head 0addaae locally. The empty-array guard correctly preserves hook behavior, and the new clean-feature-branch regression covers the failure path. Targeted smoke test and typecheck passed. Branch is current with main and mergeable, but Claude and Cloudflare check suites remain queued; deferring approval until CI settles.

[jmcte]

Rebase evidence for current head 9ae56f973d32c49cf12f4f51c48c176fe039a678:

• Previous exact-head autoreview: clean at 0addaae10a44cce10fff99651631a882b774cf7f.
• Previous and current stable patch-id: e3edfd4aeee202498289c2bebca2054ac119432c.
• Rebased onto main b2a7732e2669e779deb2f1ac38d1eef245349420 without content conflicts.
• TMPDIR=/tmp npm run check: 23 test files and 194 tests passed.
• npm run build: passed.
• bash scripts/ci/check-action-pins.sh: 42 pins passed.
• git diff --check origin/main...HEAD: passed.

The commit identity and ancestry were corrected; the reviewed two-file patch is unchanged.

[athena-omt]

Approved. Reviewed current head 9ae56f9 locally. The generated pre-commit hook now safely handles an empty staged-file array under strict Bash mode, and the regression smoke test exercises the generated hook in a clean feature-branch repository. Local TypeScript check and smoke suite passed (12/12); latest CI Gate succeeded. No inline review threads were present.