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>

Makefile

@@ -39,7 +39,7 @@ install: all
 	install -m 0755 bin/devdesk $(DESTDIR)$(PREFIX)/bin/devdesk
 	install -m 0644 libexec/devdesk-lib.sh $(DESTDIR)$(LIBDIR)/devdesk-lib.sh
 	install -m 0755 libexec/devdesk-picker libexec/devdesk-claude-run libexec/devdesk-session-hook \
-		libexec/devdesk-tmux-ready libexec/devdesk-serve $(DESTDIR)$(LIBDIR)/
+		libexec/devdesk-tmux-ready libexec/devdesk-serve libexec/devdesk-statusline $(DESTDIR)$(LIBDIR)/
 	install -m 0755 build/ttyd $(DESTDIR)$(LIBDIR)/bin/ttyd
 	install -m 0644 dist/index.html share/tmux.conf share/claude-settings.json $(DESTDIR)$(SHAREDIR)/
 	install -m 0644 etc/env $(DESTDIR)$(SYSCONFDIR)/devdesk/env