refactor(extensions): split channel runtime helper seams

scripts/lib/plugin-sdk-entrypoints.json

@@ -101,6 +101,8 @@
   "channel-config-primitives",
   "channel-config-schema",
   "channel-actions",
+  "channel-plugin-common",
+  "channel-core",
   "channel-contract",
   "channel-feedback",
   "channel-inbound",
@@ -130,6 +132,7 @@
   "realtime-transcription",
   "realtime-voice",
   "media-understanding",
+  "messaging-targets",
   "request-url",
   "runtime-store",
   "json-store",
@@ -210,6 +213,7 @@
   "string-normalization-runtime",
   "state-paths",
   "synthetic",
+  "target-resolver-runtime",
   "thread-ownership",
   "tlon",
   "tool-send",