fix: store full opencode tool output and display it in session view
- Collector sender now supports Remote-User header for forward-auth
- OpenCode parser: store full tool output (was truncated to 120 chars + first line)
- OpenCode parser: generate fallback content for tool-only turns instead of empty content
- OpenCode parser: increase parse timeout to 5min for large DBs
- Frontend: show collapsible tool output in session detail below turn body
- Frontend: extract toolOutput from both opencode ({output}) and claude-code ({content}) formats