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-autopilot-runtime/IMPLEMENTATION.md

@@ -0,0 +1,19 @@
+# IMPLEMENTATION.md — Autopilot Runtime
+
+## Changes Made
+- Created `scripts/autopilot.py` — a real Python implementation replacing the pseudocode `drive_all()` loop
+- Added stuck-task detection to `status.py --audit` as Category 5
+
+## autopilot.py Commands
+- `--summary`: Shows project task overview (total, terminal, blocked, unblocked, stuck)
+- `--drive`: Drives one step — finds the most advanced unblocked task and outputs next instructions
+- `--loop`: Runs continuous drive loop with configurable iterations and delay
+- `--stuck`: Detects tasks stuck in non-terminal phases >N minutes (default: 60)
+
+## How It Works
+- `scan_all_tasks()` reads .state files from all task directories
+- `is_terminal()` checks for complete/human_intervention phases
+- `needs_user_input()` detects approval gates and VERDICT.md with FAIL/NEEDS_REVIEW
+- `sort_by_advancement()` prioritizes tasks closest to completion
+- `detect_stuck_tasks()` finds tasks unchanged >60 minutes in non-terminal phases
+- Empty queue outputs actionable instructions to create new tasks