Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

Implement the two main UI components for the session explorer:
- SessionExplorerWindowController: NSSplitView window with left pane
  containing search field and bookmark/session list table view
- SessionExplorerTimelineController: right pane with session header
  (Resume/Fork buttons) and vertical timeline of conversation turns
  with bookmark toggling and fork-at-point support

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

…nce, safety)

- BookmarkManager: add dateDecodingStrategy = .iso8601 so bookmarks survive restart
- SessionExplorerWindowController: clear associated object in windowWillClose to break retain cycle
- SessionExplorerWindowController: guard against nil window in promptForBookmarkLabel (removes force unwrap)
- ContextMonitor.listSessions: revert to head-only read (8192 bytes) for first message; set messageCount to 0 for lazy computation
- SummaryManager: move readDataToEndOfFile() before waitUntilExit() to prevent pipe deadlock
- SidebarController: remove dead ResumeSessionInfo class and resumeSessionMenuAction method

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

…aries

…tings support

…wrapping, fix fork icon rotation

…ued sessions, show below timestamp in sidebar

…of Folder (Cmd+Opt+U)

…sage

…ely below

…rename button to Summarize with Haiku

…ing summarization

…sting explorer to front

…n opening explorer

…lter

…timeline header only

…roll jump

…kmark highlight

…session titles

…ookmarks

…entire list

…limit, preserve sidebar scroll on summarize

…selection

…mary from sidebar