[TheGreatAxios]

Closes CL-11975

Closes #34

What changed

• registerToolCallBlock stores each function_call item's real call_id and tracks hasEmittedArgs when response.output_item.added registers the block.
• inference.tool_call.delta events (both streaming and non-streaming parseJSONResponse) now carry the real callId alongside index.
• When response.output_item.added carries a non-empty item.arguments string on a function_call, parseResponse immediately emits inference.tool_call.delta and marks hasEmittedArgs.
• Handles response.function_call_arguments.done and response.output_item.done (item.type === "function_call") as fallback argument sources when no prior argument delta was emitted for that item_id, preventing parallel tool calls from finalizing with empty {} arguments while avoiding duplicate emission when deltas already streamed.
• Both done envelopes now throw ProtocolMismatchError for a function_call never announced by output_item.added (previously ignored, silently dropping the call), matching the existing .delta rule.

Verification

• bun run check (typecheck, lint, format, 55 unit tests) passes.
• bun run test:e2e (6 e2e tests through runInference) passes.
• bun run build succeeds cleanly.

[linear-code]

CL-11975