test(plugins): use in-tree sources without hash pins

Use the in-tree plugins directly for consumer contracts and avoid per-edit hash refreshes.

plugins/MIGRATION.md

@@ -20,10 +20,12 @@ remain historical evidence, not certification of newly built packages.
   installation, configuration and Marketplace publication remain independent.
 - Each plugin retains its dependency declarations and test environment. Core's
   pytest configuration and pre-commit formatting do not apply to plugin suites.
-- Core consumer tests use this checkout's `plugins/` and integrity-checked files
-  in `tests/fixtures/legacy_plugin_identity_sources.json`. Refresh the relevant
-  hashes deliberately when changing those consumer contracts. Published SDK
-  compatibility continues to be tested by the independent plugin workflows.
+- Core consumer tests use this checkout's `plugins/` directly when the source lock
+  is marked `in-tree`; the listed files are required to exist, but their contents
+  are not pinned so ordinary plugin changes do not require fixture updates.
+  Hashes remain available for externally provisioned, revision-pinned sources.
+  Published SDK compatibility continues to be tested by the independent plugin
+  workflows.
 - Core wheels, sdists, Docker contexts, release ZIPs and fnOS staging exclude
   this tree and `.lbpkg` files. Git export archives exclude this tree as well;
   a normal Git checkout still contains all plugin sources.

plugins/scripts/test_repository.py

@@ -137,6 +137,11 @@ class RepositoryTests(unittest.TestCase):
         lock = json.loads((CORE / 'tests/fixtures/legacy_plugin_identity_sources.json').read_text())
         self.assertEqual(lock['root'], 'plugins')
         self.assertEqual(lock['repository'], 'langbot-app/LangBot')
+        if lock.get('revision') == 'in-tree':
+            for key in ('files', 'local_agent_files'):
+                for relative in lock[key]:
+                    self.assertTrue((ROOT / relative).is_file(), relative)
+            return
         for key in ('files', 'local_agent_files'):
             for relative, expected in lock[key].items():
                 self.assertEqual(hashlib.sha256((ROOT / relative).read_bytes()).hexdigest(), expected, relative)