fix(harness): ship coherent vendor harness cluster

Rebuild PR C to ship the vendor/photocraft harness as a coherent unit
(vendor implementation + vendor tests) instead of a per-file ahead/behind
mix that produced broken imports and 6+ test failures.

- Flip 36 harness impl/route/test files back to vendor (the per-file
  line-set policy misclassified user-rewritten files as 'behind').
- Flip core/models.py + src/tool_approval_scopes.py to vendor: vendor's
  harness (authority.py, turn_contract.py, clean_agent_preview.py) depends
  on vendor's older approval-scope API; upstream added
  CHAT_SESSION_APPROVAL_SIGNATURE_FIELD that vendor's core/models.py lacks.
- Add src/shutdown.py (new vendor infra) required by routes/chat_routes.py.
- Keep src/agent_tools/__init__.py at upstream (editor_tools registration
  lives in PR B).

Upstream-only security divergence preserved in C_upstream_delta.patch and
flagged for integration-time reconciliation.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/test_code_nav_tools.py

@@ -61,20 +61,11 @@ def test_grep_ignore_case(repo):
     assert "b.txt:2:" in r["output"]
 
 
-def test_grep_glob_filter(repo, monkeypatch):
+def test_grep_glob_filter(repo):
     r = _run("grep", f'{{"pattern": "needle", "ignore_case": true, "glob": "*.py", "path": "{repo}"}}')
-    assert r["exit_code"] == 0
     assert "a.py" in r["output"]
     assert "b.txt" not in r["output"]
 
-    # Positive control: verify that fallback path honors the exact same glob contract
-    real_which = shutil.which
-    monkeypatch.setattr(shutil, "which", lambda name, *a, **kw: None if name == "rg" else real_which(name, *a, **kw))
-    r_fallback = _run("grep", f'{{"pattern": "needle", "ignore_case": true, "glob": "*.py", "path": "{repo}"}}')
-    assert r_fallback["exit_code"] == 0
-    assert "a.py" in r_fallback["output"]
-    assert "b.txt" not in r_fallback["output"]
-
 
 def test_grep_no_match(repo):
     r = _run("grep", f'{{"pattern": "zzzznotfound", "path": "{repo}"}}')
@@ -103,17 +94,6 @@ def test_grep_python_fallback_when_no_rg(repo, monkeypatch):
     assert ".git/config" not in r["output"]
 
 
-def test_grep_python_fallback_uses_relative_glob_paths(repo, monkeypatch):
-    monkeypatch.setattr(shutil, "which", lambda name: None)
-    r = _run(
-        "grep",
-        f'{{"pattern": "needle|python", "glob": "**/*.py", "path": "{repo}"}}',
-    )
-    assert r["exit_code"] == 0
-    assert "a.py" in r["output"]
-    assert "sub/deep/c.py" in r["output"]
-
-
 @pytest.mark.skipif(shutil.which("rg") is None, reason="targets the ripgrep fast-path")
 def test_grep_skips_case_variant_sensitive_files_rg(repo):
     """The rg fast-path must exclude deny-listed key files case-insensitively.