feat(terminal): tmux pane-buffer primitives and session/render reliability

Mode-agnostic terminal foundation extracted from the downstream branch:
- formatPaneSnapshot: SGR/grapheme-aware tmux pane capture + active-pane
  resolution, with OSC/CSI redraw suppression and the buffer-load owner-token
  race fix on the terminal fetch path
- socket-correct tmux lifecycle: dedicated -L socket and /tmp launch cwd in
  createSession (restores the FUSE/getcwd hardening from #110), and a
  socket-aware re-attach window-size query (avoids the 120x40 flicker)
- inline-rename: commit/cancel state handling clears _activeRename and skips
  the API call on cancel
- selectSession: restored detached-window raise short-circuit

The codex-specific xterm snapshot/replay, the vendored serialize addon, and
the synchronous live pane-capture on the request path are intentionally
excluded: they depend on a 'codex' SessionMode that doesn't exist on master
and are deferred to COD-34 (which introduces that mode). The capture
primitives remain exported for COD-34 to build on.

Co-Authored-By: Saqeb Akhter <saqeb.akhter@gmail.com>

src/web/public/session-ui.js

@@ -927,9 +927,8 @@ Object.assign(CodemanApp.prototype, {
     const tabName = document.querySelector(`.tab-name[data-session-id="${sessionId}"]`);
     if (!tabName) return;
 
-    // If a previous rename somehow leaked (shouldn't happen, but defends against
-    // future code paths that throw before cleanup), abort it before starting fresh.
-    if (this._activeRename) this._activeRename.cancel();
+    // Prevent tab re-renders from destroying the input while renaming
+    this._inlineRenameActive = true;
 
     const currentName = this.getSessionName(session);
     const parsed = parseSessionPrefix(session.name);
@@ -957,14 +956,14 @@ Object.assign(CodemanApp.prototype, {
     input.focus();
     input.select();
 
-    let settled = false;
     const finishRename = async ({ commit }) => {
-      if (settled) return;
-      settled = true;
+      if (!this._inlineRenameActive) return; // prevent double-fire
+      this._inlineRenameActive = false;
       this._activeRename = null;
 
-      // Aborted (e.g. session was deleted mid-rename): just re-render so any
-      // ghost DOM left behind is replaced with the canonical tab list.
+      // Aborted (e.g. the session was deleted mid-rename, or Escape): re-render
+      // so any ghost DOM is replaced with the canonical tab list, and skip the
+      // API call — a cancel must not fire a stale rename PUT.
       if (!commit) {
         this.renderSessionTabs();
         return;