Parent: #6871 | Epic: #6870

Description

Create new logging handlers that subscribe to Copilot SDK SessionEvent stream instead of langchaingo callbacks.Handler.

Tasks

• Create internal/agent/logging/session_event_handler.go
  • Thought logger: filter events for thought/reasoning content, emit to thought channel
  • File logger: write all session events to daily log file
  • Composite handler: chain multiple handlers
• Map SDK SessionEventType to current UX rendering:
  • assistant.message → thought display
  • tool.start / tool.end → tool execution display
  • error → error display
• Preserve daily log file format (azd-agent-YYYY-MM-DD.log)
• Unit tests

New File

• internal/agent/logging/session_event_handler.go