feat: free-form sessions, rename/end from the panel, live Claude Context (0.2.0)

- Sessions no longer need a project folder: any name works and starts in
  DEVDESK_DEFAULT_DIR unless it matches a project; `devdesk new NAME [PROJECT]`.
- Rename (✎) and end/forget (×) sessions from the Sessions panel, plus
  `devdesk rename`. The browser runs them as `devdesk attach --new|--rename|--end`
  through ttyd. Renames keep the running Claude and its recorded conversation:
  the hook, the run-wrapper and the statusline ask tmux for the current name.
- Claude Context panel is live: devdesk-statusline snapshots model,
  context-window use, cost and edits per session, which --list reports;
  Claude's footer gets a one-line summary. The panel now sits under Sessions.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

etc/env

@@ -12,6 +12,9 @@ DEVDESK_BIND=
 DEVDESK_PROJECTS_ROOT=/root/code
 DEVDESK_DEFAULT_SESSION=main
 
+# Where sessions that are not a project folder start (e.g. ops sessions); empty = projects root.
+DEVDESK_DEFAULT_DIR=
+
 # Claude Code binary and extra arguments for every session.
 CLAUDE_BIN=/root/.local/bin/claude
 CLAUDE_ARGS=