Merge PR #44: feat(relay) conversation history, workspace hierarchy, shell panes, pane activity

Adds relay/transcript.py — reads agent conversation transcripts (Claude JSONL)
behind get_history, replacing the nonexistent 'herdr agent history' call.
Fixes #49. Configurable via HERDR_CLAUDE_ROOTS / HERDR_TRANSCRIPT kill switch.

Also adds: real workspace/spaces hierarchy, shell pane support, pane activity,
and focus/rename_tab/close_tab/rename_agent handlers.

Supersedes PR #50 (wuqicyber's inline session-log reader) — transcript.py does
the same JSONL read but with UUID lookup (avoids cwd-drift), remote roots, and
tests.

Conflict resolution: kept #41's request_id echo on agent_prompt alongside #44's
new focus handler. Thanks @nickrunning!