fix(controller): production client_instance_id launch path and instance-aware mutation gate

Remediate review 655 blockers on PR #979 (issue #978):

B1 — Production launcher (mcp_application_launcher) mints one trusted
client_instance_id per application launch and propagates it to all five
namespace workers via GITEA_MCP_CLIENT_INSTANCE. launcher_entry and
multi_namespace_launcher_entries use that path. Workers never invent a
trusted ID; missing/malformed/user-supplied values fail closed.

B2 — _check_mcp_runtimes_diagnostics is instance-aware: two legitimate
instances sharing a profile are allowed when each has a distinct trusted
client_instance_id; duplicate workers for the same (instance, profile)
still fail closed. Worker identity/generation exported for peer scans.

Tests cover shared ID across five namespaces, distinct launches, multi-
instance same profile, same-instance duplicates, untrusted attribution,
and the production launcher path.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

tests/test_config_menu.py

@@ -175,8 +175,21 @@ class TestLauncherSnippets(unittest.TestCase):
     def test_only_safe_keys_no_secrets(self):
         entry = gitea_config.launcher_entry("prgs", "/cfg/profiles.json")["gitea-tools"]
         self.assertEqual(set(entry), {"command", "args", "env"})
-        self.assertEqual(set(entry["env"]), {"GITEA_MCP_CONFIG", "GITEA_MCP_PROFILE", "GITEA_CLIENT_MANAGED"})
+        # #978 B1: production launcher also injects trusted client identity.
+        required = {
+            "GITEA_MCP_CONFIG",
+            "GITEA_MCP_PROFILE",
+            "GITEA_CLIENT_MANAGED",
+            "GITEA_MCP_CLIENT",
+            "GITEA_MCP_CLIENT_INSTANCE",
+            "GITEA_MCP_INSTANCE_PROVENANCE",
+        }
+        self.assertTrue(required.issubset(set(entry["env"])), entry["env"])
         self.assertEqual(entry["env"]["GITEA_MCP_PROFILE"], "prgs")
+        self.assertTrue(
+            entry["env"]["GITEA_MCP_CLIENT_INSTANCE"].startswith("inst-"),
+            entry["env"]["GITEA_MCP_CLIENT_INSTANCE"],
+        )
         blob = json.dumps(entry).lower()
         for word in ("token", "password", "secret"):
             self.assertNotIn(word, blob)