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__/lanes-api.test.js

@@ -482,10 +482,11 @@ describe("lane start input", () => {
       assert.equal(created[created.indexOf("-s") + 1], `agenthub-lane-${id}-1`);
       assert.equal(created[created.indexOf("-c") + 1], cwd);
       // After `--` only the fixed size-wait wrapper that execs the user's own
-      // default shell (issue #55) — nothing from the request.
+      // default shell (issue #55) in the lane's folder (#69) — nothing from
+      // the request.
       const argv = created.slice(created.indexOf("--") + 1);
       assert.deepEqual(argv.slice(0, 2), ["sh", "-c"]);
-      assert.equal(argv.length, 3);
+      assert.deepEqual(argv.slice(3), ["sh", cwd]);
       assert.match(argv[2], /exec "\$SHELL" -l$/);
       assert.ok(!created.includes("ignored"));
       const lane = (await request("GET", `/api/lanes/${id}`)).body.lane;