feat: migrate WebRTC signaling from WebSocket to Ably pub/sub

[robbie-anam]

Summary

This PR migrates the WebRTC signaling infrastructure from a custom WebSocket implementation to Ably's pub/sub messaging platform.

Changes

• Replace custom WebSocket SignallingClient with Ably Realtime implementation
• Remove heartbeat logic as Ably handles connection health automatically
• Update ClientConfigResponse to use ablyToken and ablyChannel
• Hardcode Ably channel rewind parameter to 100 messages
• Defer connection initialization to connect() method for better resource management
• Add proper error handling for uninitialized connections
• Remove message buffering in favor of explicit connection errors
• Add Ably SDK v2.9.0 dependency

Benefits

• Improved reliability with Ably's managed infrastructure
• Automatic reconnection handling
• Message persistence with rewind capability
• Simplified codebase without manual heartbeat management
• Better resource management with deferred connections

Testing

• Verify WebRTC connection establishment works
• Test reconnection scenarios
• Confirm error handling for premature method calls
• Validate message delivery and ordering

🤖 Generated with Claude Code

[Copilot]

Pull Request Overview

This PR migrates the WebRTC signaling infrastructure from a custom WebSocket implementation to Ably's pub/sub messaging platform, improving reliability and simplifying connection management.

• Replaces custom WebSocket SignallingClient with Ably Realtime implementation
• Removes manual heartbeat logic in favor of Ably's automatic connection health management
• Updates configuration interface to use Ably tokens and channels instead of WebSocket URLs

Reviewed Changes

Copilot reviewed 6 out of 7 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/types/signalling/index.ts	Removes SignallingURLOptions export as it's no longer needed
src/types/signalling/SignallingClientOptions.ts	Replaces WebSocket configuration with Ably token and channel name
src/types/coreApi/StartSessionResponse.ts	Updates ClientConfigResponse to provide Ably credentials instead of heartbeat settings
src/modules/SignallingClient.ts	Complete rewrite to use Ably Realtime instead of WebSocket with deferred connection initialization
src/AnamClient.ts	Updates session initialization to use new Ably-based configuration
package.json	Adds Ably SDK v2.9.0 dependency

[Copilot]

The hardcoded rewind parameter of '100' should be made configurable or at least documented with a comment explaining why this specific value was chosen.

Suggested change

	params: { rewind: '100' },
	params: { rewind: String(this.rewind) }, // Use configurable rewind value

[Copilot]

The comment about renaming userUid to sessionId on the server was removed, but the field name mismatch still exists. Consider adding back the TODO comment or creating a proper tracking item for this inconsistency.

Suggested change

	connectionDescription: localDescription,
	connectionDescription: localDescription,
	// TODO: Rename `userUid` to `sessionId` on the server to resolve this naming inconsistency.

[Copilot]

The connect() method return type changed from WebSocket to void, which is a breaking change. Consider documenting this breaking change or providing a migration guide for consumers who might have been using the returned WebSocket.

[robbie-anam]