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.

tests/test_vram_detect.py

@@ -256,6 +256,12 @@ def test_lookup_model_context_prefix_match() -> None:
     assert vram._lookup_model_context("llama-3.1-8b-instruct") == 128_000
 
 
+def test_lookup_model_context_no_false_prefix_match() -> None:
+    """phi-4-mini should NOT match phi-4 (different model, wrong context)."""
+    assert vram._lookup_model_context("phi-4-mini-instruct") == 0
+    assert vram._lookup_model_context("gpt-4o-foo-unknown") == 0
+
+
 def test_detect_model_context_ollama_probe(monkeypatch, tmp_path: Path) -> None:
     monkeypatch.setattr(vram.Path, "home", lambda: tmp_path)
     monkeypatch.setattr(