Orchestrator pattern

[gjkim42]

Add orchestrator pattern to samples.

[axon-agent]

🤖 Axon Agent @gjkim42

PR #329 is ready for review.

Added examples/05-orchestrator/ demonstrating the fan-out/fan-in orchestrator pattern:

• Two independent research Tasks run in parallel (stage 1)
• An orchestrator Task with dependsOn waits for both, then synthesizes their outputs using prompt templates (stage 2)
• Includes README with DAG diagram, template reference table, and step-by-step instructions
• Integration test verifies multi-dependency waiting behavior

All CI checks passing (build, test, verify, test-integration).