feat(agent): Add session resumption support

[edenreich]

Summary

Adds session resumption support to the agent command, allowing users to continue work from where they left off.

Changes

New Features

• --session-id flag: Resume existing agent sessions by conversation ID
• Session lifecycle events: Structured JSON status messages for session events
• Conversation loading: Load and restore full conversation history from database
• Turn counter reset: Full budget restored when resuming sessions

Implementation Details

1. convertFromConversationEntry: Reverse conversion from domain.ConversationEntry to ConversationMessage
2. loadExistingSession: Load conversation from persistent repository and restore state
3. outputStatusMessage: Output structured JSON for session lifecycle events
4. Session ID preservation: Maintain session ID for continued persistence

Documentation Updates

• Updated README.md with session resumption examples
• Enhanced commands-reference.md with detailed usage and JSON examples
• Added session resumption to feature list

Testing

• Comprehensive unit tests for convertFromConversationEntry
• Tests cover all message types: user, assistant, tool, with images, tool calls, and metadata
• Edge cases: internal messages, tool execution metadata, empty content

Usage Examples

# List conversations to find session IDs
infer conversations list

# Resume an existing session
infer agent "continue fixing the authentication bug" --session-id abc-123-def

# Resume with additional files
infer agent "analyze these new error logs" --session-id abc-123 --files error.log

# Resume without saving (testing mode)
infer agent "try a different approach" --session-id abc-123 --no-save

JSON Status Messages

// Successful resume
{"type":"info","message":"Resumed agent session","session_id":"abc-123","message_count":15,"timestamp":"2025-12-11T..."}

// Failed resume (warning)
{"type":"warning","message":"Could not load session, starting fresh","session_id":"invalid","error":"failed to load conversation: not found","timestamp":"2025-12-11T..."}

// New session
{"type":"info","message":"Starting new agent session","session_id":"new-uuid","model":"openai/gpt-4","timestamp":"2025-12-11T..."}

Benefits

• Continuity: Continue complex tasks across multiple sessions
• Context preservation: Maintain full conversation history
• Efficiency: Avoid repeating setup and context establishment
• Debugging: Easier to debug and iterate on complex problems
• Integration: Structured JSON output for automation and monitoring

Technical Notes

• Uses existing persistent conversation repository infrastructure
• Maintains backward compatibility (no breaking changes)
• All existing tests pass
• Follows existing code patterns and conventions

[ig-semantic-release-bot]

🎉 This PR is included in version 0.88.0 🎉

The release is available on GitHub release

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