fix(review): expand works_as_is_stems to cover all scripts per HookDef

works_as_is_stems used hd.scripts[0] only, missing non-first scripts of
multi-script works-as-is hooks (e.g. mcp_run_skill has 5 scripts,
dispatch_food_truck has 4). Probe rows for those scripts were recorded
in the matrix but excluded from the coverage check, allowing gaps to
pass silently.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: Trecek

tests/execution/backends/test_hook_strength_matrix.py

@@ -54,7 +54,10 @@ def test_works_as_is_hooks_have_soft_or_better() -> None:
     rows = matrix["combinations"]
 
     works_as_is_stems: set[str] = {
-        Path(hd.scripts[0]).stem for hd in HOOK_REGISTRY if hd.codex_status == "works-as-is"
+        Path(script).stem
+        for hd in HOOK_REGISTRY
+        if hd.codex_status == "works-as-is"
+        for script in hd.scripts
     }
     seen_stems: set[str] = set()
     for row in rows: