Fix 11 automation gaps: dead-end phases, autopilot runtime, guard plugin, status.py bugs, Category 3 audit

- Fix decomposition:approved and human_intervention dead-end phases
- Add scripts/autopilot.py: real drive_all() implementation
- Fix guard plugin: throw Error instead of injecting user messages
- Fix status.py: double continue, _require_state, --list-states
- Add Category 3 (git-based modification) audit
- Add Category 5 (stuck-task detection) audit
- All 206 tests pass

tasks/implement-category-3-audit/SPEC.md

@@ -0,0 +1,16 @@
+# Implement Category 3 Audit (Git-Based Modification Detection)
+
+## Problem
+Category 3 audit (status.py:698-702) is stubbed out with "future work". The framework cannot detect unauthorized modifications.
+
+## Fix
+Implement git-based modification checking:
+1. Check git diff for uncommitted changes to files outside task folders
+2. Check `git log --diff-filter=M --name-only` for recent modifications not associated with open tasks
+3. Flag files modified when no task is in implement/doc_review phase
+4. Report violations with file paths and suggested action
+
+## Verification
+- `status.py --audit` includes Category 3 findings
+- Detects unauthorized modifications
+- Separates false positives (framework files, config files)