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/IMPLEMENTATION.md

@@ -0,0 +1,12 @@
+# IMPLEMENTATION.md — Category 3 Audit
+
+## Changes Made
+- `scripts/status.py:698-703`: Replaced "future work" stub with `_audit_category3()` function call
+- `scripts/status.py:605-660`: Added `_audit_category3()` function implementing git-based modification detection
+
+## How It Works
+- Checks `git diff --name-only HEAD` and `git diff --cached --name-only HEAD` for uncommitted changes
+- Excludes files inside task folders (those are legitimate workflow artifacts)
+- If no task is in implement/doc_review phase, all uncommitted changes outside task folders are flagged as violations
+- If active edit tasks exist, changes outside task folders are reported as informational
+- Handles missing .git directory gracefully