feat: per-change-block hunk actions (#50), codex lanes without a pipeline, macOS LaunchAgent

- git (#50): stage-hunk/discard-hunk take an optional `block` — one run of
  consecutive +/- lines inside an @@ hunk. `onlyBlock` (server/lib/git-diff.js)
  cuts git's fresh hunk down to it, folding the other blocks into the side
  being checked; LaneDiffView hangs one review bar per block (unified + split)
  and its arrows walk blocks.
- git exclude: entries AgentHub writes for a lane go to the COMMON git dir with
  the lane's path prefix (server/lib/git-exclude.js, used by router-apply and
  lane-mcp) — a linked worktree's own info/exclude is never read by git, and a
  subdir lane has no .git. MCP sync no longer fails with ENOTDIR on a worktree
  lane or creates a stray .git in a non-repo lane.
- codex lanes carry no pipeline: codex-ingest mirrors only idle/running,
  codex-nudge is removed, agents install writes nothing for codex, the
  Workspace hides stage/pipeline/feature pickers/PipelineMap for them, and
  every server start clears leftover codex stage data and the old AGENTS.md
  stage block.
- Changes panel: a whole file opens for reading and enters the editor on a
  click on its text (caret at the clicked line), not automatically.
- macOS: LaunchAgent start-at-login (scripts/launchd-service.js, picked by
  scripts/service-manager.js).
- Adds the AgentHub introduction slides and their image-embedding script.

openapi.yaml

@@ -11253,6 +11253,9 @@ paths:
                 hunk:
                   type: string
                   description: stage-hunk, discard-hunk; the hunk's `@@` line as the diff returned it. The server re-reads the diff and applies git's own text of that hunk; a hunk no longer present is 409 EHUNKGONE.
+                block:
+                  type: integer
+                  description: stage-hunk, discard-hunk (optional); act on only the block-th run of consecutive +/- lines inside that hunk — the other runs are folded into context. Out of range is 409 EHUNKGONE.
                 context:
                   type: integer
                   description: stage-hunk, discard-hunk; the context the hunk was read at.