feat(cli): include exitCode in command tool_result events

[cte]

Summary

• Propagate the command exit code through the JSON event emitter's tool_result events so CLI consumers can distinguish between successful and failed command executions
• Add exitCode field to rooCliToolResultSchema in the types package
• Extract exit code from commandExecutionStatus in stdin-stream.ts and pass it through to emitCommandOutputDone

Test plan

• Updated existing streaming test to verify exitCode is included in tool_result events
• Verify CLI consumers receive the exitCode field in command completion events
• Run full test suite to confirm no regressions

🤖 Generated with Claude Code

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