Matrix: drop unrelated SDK cleanup

Remove the plugin-sdk, entrypoint inventory, and contract drift that got
bundled into the Matrix dispatcher compatibility PR.

Keep the PR focused on the Matrix transport fallback and the shared SSRF
fail-closed behavior so review and backports stay narrow.

scripts/lib/plugin-sdk-entrypoints.json

@@ -169,8 +169,6 @@
   "memory-core-host-runtime-files",
   "memory-lancedb",
   "msteams",
-  "music-generation",
-  "music-generation-core",
   "models-provider-runtime",
   "skill-commands-runtime",
   "native-command-registry",