fix: v2.6.1 — panes start in their folder again after an update (#69), Changes panel stacks every repo, clickable paths in chat

- #69: tmux applies a pane's `-c` only while its server's own cwd exists.
  The server was forked from the dashboard's cwd (the plugin cache dir),
  outlives updates, and the old cache dir is pruned — after that every new
  pane started in a deleted directory, where `claude` died at once ("run not
  found") and a shell printed getcwd errors. tmux calls now run from `/`,
  and the pane's sh wrapper cds into its folder itself, which also heals a
  tmux server that is already stuck.
- Changes panel: a workspace's extra folders are sections stacked under the
  workspace folder (VS Code Source Control style), with Close repository /
  Close other repositories on a header's right-click.
- Chat: URLs and absolute paths are links; Claude Code's `[Image: source:]`
  line folds into its turn; uploads under `<data dir>/drops/` are listed.
- Update check: a checkout holding commits a newer release lacks reports
  `diverged_from_release` instead of offering a fast-forward that can only fail.

server/__tests__/lane-sources.test.js

@@ -185,8 +185,8 @@ describe("lane-sources instructions and launch", () => {
     let argv = null;
     tmux.__setExecImpl((args) => {
       if (args[0] === "has-session") throw Object.assign(new Error("gone"), { status: 1 });
-      // The CLI rides behind `sh -c <wait for a client> sh` (pty-run.js).
-      if (args[0] === "new-session") argv = args.slice(args.indexOf("--") + 5);
+      // The CLI rides behind `sh -c <cd; wait for a client> sh <cwd>` (pty-run.js).
+      if (args[0] === "new-session") argv = args.slice(args.indexOf("--") + 6);
       return "";
     });
     pty.spawnRun({ laneId: lane.id, cwd: ws, initialPrompt: "-c fix it" });