refactor(mcp_client): obliterate legacy _resolve_and_check wrapper; migrate 5 callers to _resolve_and_check_result (Phase 3)

Phase 3 (1 of 9 cruft sites obliterated):

The legacy wrapper _resolve_and_check(raw_path) returned tuple[Path|None, str],
dropping the structured ErrorInfo from _resolve_and_check_result. Callers in
dispatch_tool_call (py_remove_def, py_add_def, py_move_def, py_region_wrap) used
the pattern 'p, err = _resolve_and_check(path); if err: return err' which is
exactly the false drain the user wants obliterated.

Migration:
- DELETED: _resolve_and_check wrapper (lines 175-188 in src/mcp_client.py)
- UPDATED: 5 callers in dispatch_tool_call now call _resolve_and_check_result
  directly with .ok check + NilPath check + structured error routing
- UPDATED: 4 test files that monkey-patched _resolve_and_check to mock the
  Result helper instead:
  - test_mcp_ts_integration.py (1 mock)
  - test_ts_c_tools.py (2 mocks)
  - test_ts_cpp_tools.py (8 mocks)
  - test_cruft_removal.py (NEW; 4 tests including the wrapper-obliterated
    invariant + the audit-script-finds-zero invariant + 2 dispatch tests)

Test result: 51/51 pass (31 baseline + 16 heuristic + 4 cruft).
Audit gate: src/mcp_client.py --strict exits 0 (no new violations introduced).
Baseline audit: --include-baseline --strict exits 1 only due to 4 pre-existing
non-baseline INTERNAL_RETHROW sites in outline_tool.py / warmup.py /
vendor_capabilities.py (out of scope per spec).

The wrapper IS DELETED. No pass-through. No backward compat. The dead code dies.

tests/test_cruft_removal.py

@@ -0,0 +1,84 @@
+"""Wrapper-obliteration tests for result_migration_cruft_removal_20260620.
+
+Phase 3 (mcp_client._resolve_and_check): the legacy wrapper is DELETED;
+callers in dispatch_tool_call use _resolve_and_check_result(...).ok directly.
+The test mocks _resolve_and_check_result (the proper Result helper).
+"""
+import subprocess
+from pathlib import Path
+from unittest.mock import patch
+
+import pytest
+
+from src.mcp_client import dispatch
+
+
+@pytest.fixture
+def mock_resolve_result():
+    """Mock the proper Result helper to always succeed."""
+    from src import mcp_client
+    original = mcp_client._resolve_and_check_result
+    mcp_client._resolve_and_check_result = lambda path: __import__("src").mcp_client.Result(
+        data=Path(path),
+        errors=[],
+    )
+    yield
+    mcp_client._resolve_and_check_result = original
+
+
+def test_resolve_and_check_wrapper_obliterated():
+    """Phase 3 invariant: the legacy _resolve_and_check wrapper is DELETED."""
+    from src import mcp_client
+    assert not hasattr(mcp_client, "_resolve_and_check"), (
+        "_resolve_and_check legacy wrapper must be OBLITERATED (deleted). "
+        "Callers must use _resolve_and_check_result(...).ok directly."
+    )
+
+
+def test_dispatch_py_remove_def_uses_result_helper(mock_resolve_result, tmp_path):
+    """dispatch_tool_call for py_remove_def uses _resolve_and_check_result(...).ok."""
+    from src import mcp_client
+
+    c_file = tmp_path / "test.py"
+    c_file.write_text("def foo(): pass\n")
+
+    with patch("src.mcp_client.py_struct_tools") as mock_struct:
+        mock_struct.py_remove_def.return_value = "removed"
+        # dispatch routes through _resolve_and_check_result now
+        result = dispatch("py_remove_def", {"path": str(c_file), "name": "foo"})
+        assert result == "removed", f"expected 'removed', got {result!r}"
+
+
+def test_dispatch_py_move_def_uses_result_helper(mock_resolve_result, tmp_path):
+    """dispatch_tool_call for py_move_def (multi-path) uses _resolve_and_check_result."""
+    from src import mcp_client
+
+    src_file = tmp_path / "src.py"
+    src_file.write_text("def foo(): pass\n")
+    dest_file = tmp_path / "dest.py"
+    dest_file.write_text("# dest\n")
+
+    with patch("src.mcp_client.py_struct_tools") as mock_struct:
+        mock_struct.py_move_def.return_value = "moved"
+        result = dispatch(
+            "py_move_def",
+            {
+                "src_path": str(src_file),
+                "dest_path": str(dest_file),
+                "name": "foo",
+                "dest_name": "App",
+                "anchor_type": "before",
+            },
+        )
+        assert result == "moved", f"expected 'moved', got {result!r}"
+
+
+def test_audit_script_finds_zero_mcp_client_wrappers():
+    """Phase 3 invariant: scripts/audit_legacy_wrappers.py reports 0 wrappers in src/mcp_client.py."""
+    r = subprocess.run(
+        ["uv", "run", "python", "scripts/audit_legacy_wrappers.py"],
+        capture_output=True, text=True,
+    )
+    assert "src\\mcp_client.py" not in r.stdout, (
+        f"expected 0 wrappers in src/mcp_client.py, but found:\n{r.stdout}"
+    )