feat: real-time session preview updates during conversation

[grimmerk]

Summary

Session preview text (last assistant message, first/last user prompt) currently only loads when the Sessions tab is first opened. It does not update in real-time as the conversation progresses.

Current behavior

• Status dots update in real-time (via hooks + fs.watch) ✅
• Last assistant message (blue text) only updates when session becomes idle (added in PR feat: VS Code session support + real-time preview refresh #103) ✅
• Intermediate messages (tool usage, reasoning, partial responses) are not reflected until the session completes

Desired behavior

Show intermediate updates during an active conversation:

1. Tool usage messages (e.g., "Read 1 file", "Edit file") — could show as brief activity indicators
2. Intermediate assistant text — update the blue preview text as the assistant responds
3. User messages sent mid-conversation — update the amber last-prompt text

Difficulty

• Intermediate updates require either polling the JSONL file or hooking into more granular events
• PostToolUse hook could provide tool-level updates, but firing on every tool use may be too frequent
• Streaming assistant responses are written as multiple JSONL entries that get deduplicated — reading mid-stream is complex

Suggested approach

• Start with updating on Stop event (already done in feat: VS Code session support + real-time preview refresh #103)
• Consider periodic re-read (e.g., every 5-10s) for active sessions only
• Tool-level updates could use PostToolUse hook but may add visual noise

Related

• PR feat: VS Code session support + real-time preview refresh #103 added idle-transition refresh for last assistant message
• PR feat: show assistant responses for all (first 100) sessions #98 added "show final assistant message" for all sessions
• PR feat: session status hooks (working/idle/needs-attention) #92 added session status hooks infrastructure

🤖 On behalf of @grimmerk — generated with Claude Code