chore(models): finish the opus-5 replacement — no stale opus-4 fixtures remain

Every fixture, comment example, and panel mock that presented an Opus 4.x
id as current now carries claude-opus-5 (or the current sonnet/haiku ids in
the panel usage mocks). The only deliberate claude-opus-4 survivors are the
pricing-table fragment and its tests — they price the historical usage rows,
which would otherwise re-read as $0.

tests/unit/runtime/test_spawn_manifest.py

@@ -104,7 +104,7 @@ class TestWriteManifest:
                 role="developer",
                 team="backend",
                 workspace_path=tmp_path,
-                agent_model="claude-opus-4-7",
+                agent_model="claude-opus-5",
             )
         )
         manifest_path = tmp_path / "tool-manifest.json"