Add read-only workspace and branch metadata to runtime thread summaries so VS Code Agent View can show when a thread lane is on another branch. Non-git workspaces return null branch metadata instead of failing.
Refs #2580, #2721.
Credits the existing branch-visibility trail from #1217/#2341 in the changelog.
Harvests the safe Phase 0 VS Code lane from PR #1022 and the Agent View request in #2580 while keeping chat webviews, inline edits, Agent View, and retry/undo runtime endpoints out of this slice.
Credits @lbcheng888 for the earlier extension scaffold and @AiurArtanis plus the v0.9 GUI/VS Code reporters for the request trail.
Hunter B