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/lib/update-check.js

@@ -698,6 +698,16 @@ async function getUpdatesStatus(gitRoot = DEFAULT_ROOT, options = {}) {
       `This dashboard runs from the Claude Code plugin cache (marketplace '${pluginInstall.marketplace}'), ` +
       `so it can't update itself. Run the commands above, then '/reload-plugins' in Claude Code — ` +
       `or just run '/agenthub-update', which does both and rebuilds the runtime.`;
+  } else if (release.ok && releaseIsNewer && commitsAheadOfRelease > 0) {
+    // HEAD carries commits the release lacks (e.g. local wip that the release
+    // squashed into a new commit): `merge --ff-only` can only fail, and how to
+    // reconcile is the user's call, so fetch the tag and say why.
+    situation = "diverged_from_release";
+    manualParts = [`cd "${root}"`, `git fetch ${canonicalRemote} --tags`];
+    situationNote =
+      `Your checkout has ${commitsAheadOfRelease} commit(s) that release ${release.tag} doesn't contain, ` +
+      `so it can't be fast-forwarded. If they're already in the release, move onto it with ` +
+      `'git reset --keep ${release.tag}'; otherwise merge or rebase onto ${release.tag}.`;
   } else if (release.ok && releaseIsNewer) {
     // Move onto the release TAG rather than the branch tip: the tag is what
     // was published, and a fast-forward keeps the tracking branch intact (a