refactor: consolidate meeting and media provider families (#126053)

* refactor(plugins): consolidate provider family helpers

* fix(plugin-sdk): keep meeting script helpers private

* fix(plugins): sync meeting boundary paths

scripts/lib/plugin-sdk-entrypoints.json

@@ -240,6 +240,7 @@
   "realtime-voice-audio-queue",
   "realtime-voice-activation",
   "realtime-voice",
+  "meeting-page-script-runtime",
   "meeting-runtime",
   "transcripts",
   "media-understanding",

scripts/lib/plugin-sdk-private-local-only-subpaths.json

@@ -65,6 +65,7 @@
   "llm",
   "markdown-table-runtime",
   "media-generation-runtime",
+  "meeting-page-script-runtime",
   "memory-core-host-embedding-registry",
   "memory-core-host-engine-curated",
   "memory-core-host-engine-embeddings",