Summary

Add support for ingesting Pi Coding Agent session artifacts as an agent rollout seed source.

Pi sessions are tree-structured JSONL files stored at ~/.pi/agent/sessions/. The handler resolves the active conversation path by walking from the last entry back to the root via id/parentId links, then normalizes all message types into the shared rollout schema.

Key design points

• Tree-structured sessions — Pi is the first format with in-place branching; the handler resolves the active path automatically
• Entry-level types — model_change, compaction, branch_summary, custom_message, and thinking_level_change are handled alongside message entries
• Message roles — user, assistant (with inline ToolCall/ThinkingContent/TextContent blocks), toolResult, bashExecution (synthesized as tool-call pairs), custom, compactionSummary, branchSummary
• Shared utility — extracted normalize_message_content to utils.py (was duplicated in Hermes handler)

Format reference

• Pi session format docs