fix(server): cast finished listener call, remove stale TODO, document execute contract

[JakubWorek]

Description

Three small SDK quality fixes surfaced while reviewing the codebase:

SDK changes

• execution_event_bus: Cast listener.call(this) for 'finished' listeners (which are invoked with no args despite the typed Listener signature). Clears 2 TS strict-mode issues; .betterer.results regression baseline shrinks accordingly.
• jsonrpc_transport_handler: Removed stale TODO about mid-stream SSE errors; the Express layer already catches and writes formatSSEErrorEvent (covered by express_app.spec.ts).
• AgentExecutor.execute JSDoc: Documented the contract that every streaming turn must begin with a task or message event (including follow-ups). The server already enforces this; the JSDoc just makes it explicit to implementors.

[github-actions]

🧪 Code Coverage

⬇️ Download Full Report

	Base	PR	Delta
src/compat/v0_3/server/transports/jsonrpc/jsonrpc_transport_handler.ts	97.11%	100%	🟢 +2.89%
src/server/transports/jsonrpc/jsonrpc_transport_handler.ts	78.89%	80.95%	🟢 +2.06%
Total	90.73%	90.84%	🟢 +0.11%

Generated by coverage-comment.yml

[gemini-code-assist]

Code Review

This pull request addresses TypeScript strict-mode compiler errors in execution_event_bus.ts by adding type casts, updates documentation in agent_executor.ts regarding event publishing requirements, and refactors comments in jsonrpc_transport_handler.ts. The reviewer provided valuable feedback, suggesting method overloading in ExecutionEventBus to achieve proper type safety without casting, and recommending the removal of a redundant console.error call in the JSON-RPC transport handler to prevent duplicate server logs.

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