fix: allow taskless hotfix closure

[MageByte-Zero]

Summary

• add a hotfix-specific executing -> closing guard mapping
• allow reviewed hotfixes to close without a tasks.md
• retain test, spec-sync, execution-plan, and review-receipt gates
• add an end-to-end regression test using real execution evidence

Root cause

Hotfixes had no workflow-specific closing transition checks, so the guard fell back to the full-workflow checks and incorrectly required tasks-complete, even though tasks.md is optional for the hotfix path.

Verification

• node --test tests/lib/guard.test.mjs — 35/35 passed
• npm run build — passed
• npm test — 489/489 passed
• node --check scripts/guard/guard.mjs — passed
• git diff --check 2d5c92a..HEAD — passed
• real taskless-hotfix transition: executing -> closing — passed
• independent review — PASS, no findings

Closes #71