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.

scripts/migrate-project.sh

@@ -105,7 +105,7 @@ while IFS= read -r -d '' project_file; do
     MOVED+=("$rel_path -> extensions/$(basename "$rel_path")")
     echo "  MOVED    $rel_path → extensions/$(basename "$rel_path") (customized)"
   fi
-done < <(find "$PROJECT_AUTOMATON" -maxdepth 1 -type f -name "*.md" -o -name "*.sh" -print0 2>/dev/null || true)
+done < <(find "$PROJECT_AUTOMATON" -maxdepth 1 -type f \( -name "*.md" -o -name "*.sh" \) -print0 2>/dev/null || true)
 
 # Task directory — tasks always live in .automaton/tasks/ for all modes
 ROOT_TASKS="$PROJECT_DIR/tasks"