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.

src/mcp_client.py

@@ -172,21 +172,7 @@ def _is_allowed(path: Path) -> bool:
    return True
  return False
 
-def _resolve_and_check(raw_path: str) -> tuple[Path | None, str]:
- """
- Resolve raw_path and verify it passes the allowlist check.
- Returns (resolved_path, error_string).  error_string is empty on success.
-
- Thin wrapper over _resolve_and_check_result; the legacy (Path|None, str)
- tuple shape is preserved for backward compatibility, but the try/except
- handling now lives in the Result variant (where it can return ErrorInfo
- with the structured kind/message/original fields).
- """
- resolved = _resolve_and_check_result(raw_path)
- if resolved.ok and not isinstance(resolved.data, NilPath):
-  return resolved.data, ""
- return None, "; ".join(e.ui_message() for e in resolved.errors)
- # ------------------------------------------------------------------ tool implementations
+# ------------------------------------------------------------------ tool implementations
 
 def search_files(path: str, pattern: str) -> str:
  """
@@ -1823,12 +1809,20 @@ def dispatch(tool_name: str, tool_input: dict[str, Any]) -> str:
  if tool_name == "ts_cpp_update_definition":
   return ts_cpp_update_definition(path, str(tool_input.get("name", "")), str(tool_input.get("new_content", "")))
  if tool_name == "py_remove_def":
-  p, err = _resolve_and_check(path)
-  if err: return err
+  resolved = _resolve_and_check_result(path)
+  if not resolved.ok:
+   return "; ".join(e.ui_message() for e in resolved.errors)
+  if isinstance(resolved.data, NilPath):
+   return "; ".join(e.ui_message() for e in resolved.errors)
+  p = resolved.data
   return py_struct_tools.py_remove_def(str(p), str(tool_input.get("name", "")))
  if tool_name == "py_add_def":
-  p, err = _resolve_and_check(path)
-  if err: return err
+  resolved = _resolve_and_check_result(path)
+  if not resolved.ok:
+   return "; ".join(e.ui_message() for e in resolved.errors)
+  if isinstance(resolved.data, NilPath):
+   return "; ".join(e.ui_message() for e in resolved.errors)
+  p = resolved.data
   return py_struct_tools.py_add_def(
    str(p), 
    str(tool_input.get("name", "")), 
@@ -1837,23 +1831,26 @@ def dispatch(tool_name: str, tool_input: dict[str, Any]) -> str:
    tool_input.get("anchor_symbol")
   )
  if tool_name == "py_move_def":
-  p_src, err = _resolve_and_check(str(tool_input.get("src_path", "")))
-  if err: return err
-  p_dest, err = _resolve_and_check(str(tool_input.get("dest_path", "")))
-  if err: return err
+  resolved_src = _resolve_and_check_result(str(tool_input.get("src_path", "")))
+  if not resolved_src.ok or isinstance(resolved_src.data, NilPath):
+   return "; ".join(e.ui_message() for e in resolved_src.errors)
+  resolved_dest = _resolve_and_check_result(str(tool_input.get("dest_path", "")))
+  if not resolved_dest.ok or isinstance(resolved_dest.data, NilPath):
+   return "; ".join(e.ui_message() for e in resolved_dest.errors)
   return py_struct_tools.py_move_def(
-   str(p_src),
-   str(p_dest),
+   str(resolved_src.data),
+   str(resolved_dest.data),
    str(tool_input.get("name", "")),
    str(tool_input.get("dest_name", "")),
    str(tool_input.get("anchor_type", "")),
    tool_input.get("anchor_symbol")
   )
  if tool_name == "py_region_wrap":
-  p, err = _resolve_and_check(path)
-  if err: return err
+  resolved = _resolve_and_check_result(path)
+  if not resolved.ok or isinstance(resolved.data, NilPath):
+   return "; ".join(e.ui_message() for e in resolved.errors)
   return py_struct_tools.py_region_wrap(
-   str(p),
+   str(resolved.data),
    int(tool_input.get("start_line", 1)),
    int(tool_input.get("end_line", 1)),
    str(tool_input.get("region_name", ""))