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>

libexec/devdesk-session-hook

@@ -7,13 +7,14 @@
 # shellcheck source=libexec/devdesk-lib.sh
 . "${DEVDESK_LIBEXEC:-/usr/lib/devdesk}/devdesk-lib.sh" || exit 0
 
-[ -n "${DEVDESK_SESSION:-}" ] || exit 0
-dd_valid_name "$DEVDESK_SESSION" || exit 0
+session=$(dd_current_session)
+[ -n "$session" ] || exit 0
+dd_valid_name "$session" || exit 0
 
 input=$(cat)
 id=$(jq -r '.session_id // empty' <<<"$input" 2>/dev/null)
 source=$(jq -r '.source // empty' <<<"$input" 2>/dev/null)
 [ -n "$id" ] || exit 0
 
-dd_registry_set_claude "$DEVDESK_SESSION" "$id" "$source" 2>/dev/null
+dd_registry_set_claude "$session" "$id" "$source" 2>/dev/null
 exit 0