build(core): emit the core entry's declarations with @internal stripped
The core rollup build had declaration: false, so its stripInternal had
nothing to act on and the entry's types came from the main build. It now
emits its own declarations to dist/core/types, and package.json points
the core entry (and its downlevel copy) there. The main entry keeps its
@internal members for the packages that use them.
stripInternal removes whatever is tagged, so symbols that public
signatures name lose their tag: ExtensionContext, installExtensions,
InternalRoomOptions, the RTCEngine, PCTransport, SignalClient and
OutgoingDataStreamManager classes, getLogger, getBrowser, VideoPublisher
and LocalParticipantSlots. BaseE2EEManager tags the same members as
E2EEManager, and rpc/index.ts no longer re-exports internal helpers.
pnpm check:core type-checks the stripped declarations with skipLibCheck
off, so a dangling reference fails the gate.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>