Fix 10 audit bugs: path prefix matching, verdict parsing, CORS, stale-task detection, phase mapping

Batch 1 (High severity):
- Bug 1: --audit cat3 now checks .automaton/tasks/ paths
- Bug 4: Verdict PASS/FAIL uses structured ## Status: line parsing
- Bug 5: register-guards.sh checks .json/.jsonc, writes plugin key, strips comments
- Bug 7: --can-edit/--scope-check path prefix uses os.sep boundary

Batch 2 (Medium/Low severity):
- Bug 2: migrate-project.sh find command parentheses for -prune binding
- Bug 3: vram_detect model prefix matching with known-suffix whitelist
- Bug 6: dashboard reads .state file before artifact heuristic fallback
- Bug 8: removed wildcard CORS, added security headers (nosniff, DENY)
- Bug 9: stale-task detection uses .state.lastedit instead of .state mtime
- Bug 10: TEST_PLAN.md maps to test_design (was implement)

249 tests pass (up from 235). All 10 tasks driven through full workflow to completion.

tasks/fix-test-plan-phase-mapping/IMPLEMENTATION.md

@@ -0,0 +1,22 @@
+# Implementation: fix-test-plan-phase-mapping
+
+## Bug
+Both `status.py:_infer_state_from_artifacts()` and the dashboard's `determine_task_state()` mapped `TEST_PLAN.md` to the `implement` phase. But `TEST_PLAN.md` is produced during the `test_design` phase, not `implement`. This caused:
+- `--upgrade` to bootstrap incorrect `.state` for tasks with TEST_PLAN.md
+- Dashboard to show `IMPLEMENT` instead of `TEST_DESIGN` for tasks that have a test plan but no implementation yet
+
+## Fix
+Changed the mapping in both locations:
+1. `scripts/status.py:348-349`: `TEST_PLAN.md` → `test_design` (was `implement`)
+2. `automaton/dashboard/core/task.py:548-549`: `TEST_PLAN.md` → `TaskState.TEST_DESIGN` (was `TaskState.IMPLEMENT`)
+
+## Files Changed
+- `scripts/status.py` (line 348-349): Changed return value from `"implement"` to `"test_design"`
+- `automaton/dashboard/core/task.py` (line 548-549): Changed return from `TaskState.IMPLEMENT` to `TaskState.TEST_DESIGN`
+- `tests/test_task.py`: Updated `test_implementation_from_test_plan` and `test_test_plan_shows_implement` to assert `TEST_DESIGN` instead of `IMPLEMENT`
+
+## Tests
+- `test_implementation_from_test_plan`: Now asserts `TaskState.TEST_DESIGN`
+- `test_test_plan_shows_test_design` (renamed from `test_test_plan_shows_implement`): Asserts `TaskState.TEST_DESIGN`
+- `test_test_plan_maps_to_test_design` in `test_status.py`: Verifies `--upgrade` infers `test_design` for TEST_PLAN.md
+- All 249 tests pass