fix(harness): address Copilot/CodeRabbit review nits

- local_harness: fail fast (exit 2) on empty --legs and on --ci without
  UNITY_IMAGE, instead of silently exiting green / crashing with an
  unhandled CalledProcessError
- local_harness: correct the nearest-patch `best` type annotation
  (key is (patch:int, suffix:str), not a 3-tuple)
- test_tool_test_symmetry: fix the module docstring to match behavior
  (only test_*.py files are scanned; non-test_*.py scripts like
  tests/e2e/bridge_smoke.py do not count toward coverage)

Deferred CodeRabbit's SHA-pin suggestion for e2e-bridge.yml: the repo pins
actions by tag (@v4/@v6), not SHA, so pinning one workflow would be
inconsistent — left as a repo-wide policy decision.

Author: Scriptwonder

Server/tests/test_tool_test_symmetry.py

@@ -2,9 +2,10 @@
 
 Enforces the CLAUDE.md rule that "Every new feature needs tests". A tool module
 (any file under ``services/tools/`` that exposes an ``@mcp_for_unity_tool``) is
-considered covered when any file under ``Server/tests/`` references it by module
-name -- a dedicated ``test_<module>.py``, a characterization test, or an
-integration test all count.
+considered covered when a ``test_*.py`` file under ``Server/tests/`` references it
+by module name -- a dedicated ``test_<module>.py`` or a characterization test
+counts. Non-``test_*.py`` scripts (e.g. ``tests/e2e/bridge_smoke.py``) are not
+scanned, so a tool exercised only there still needs a unit/characterization test.
 
 Tools that are genuinely untested today live in ``KNOWN_UNTESTED`` so this guard
 fails for *new* untested tools without forcing a full backfill first. SHRINK the

tools/local_harness.py

@@ -382,7 +382,7 @@ def discover_editor(version: str,
     if sec:
         roots.append(sec)
 
-    best: tuple[tuple[int, int, str], str, str] | None = None  # ((patch, suffix-as-key), binary, dir_version)
+    best: tuple[tuple[int, str], str, str] | None = None  # ((patch, suffix), binary, dir_version)
     for root in roots:
         try:
             entries = _listdir(root)
@@ -1349,8 +1349,15 @@ def main(argv: list[str] | None = None) -> int:
     args = build_arg_parser().parse_args(argv)
 
     legs = parse_legs(args.legs)
+    if not legs:
+        print("::error:: --legs did not include any valid values (allowed: smoke,editmode,playmode)")
+        return 2
     if args.ci:
         args.no_warmup = True
+        if not os.environ.get("UNITY_IMAGE"):
+            print("::error:: --ci requires the UNITY_IMAGE environment variable "
+                  "(the unityci/editor image to run the headless Editor in)")
+            return 2
 
     # Resolve project path (repo-relative or absolute).
     project_path = Path(args.project_path)