feat: v0.6.0 light mode, command palette, dialogs, toasts

- Light mode with the house ☀/◐ toggle and lt_theme preference; light
  terminal palette; Claude runs with dark-ansi so its colours follow the
  palette; tmux and the statusLine use ANSI colours.
- Command palette (⌕, Ctrl+Shift+P) with session, terminal, view, link and
  help commands.
- .lt-modal dialogs for new/rename/end and a keyboard shortcuts sheet.
- .lt-toast results for actions, uploads, copy and CI.
- ttyd dropped the reply of fast one-shot commands; replies now wait for the
  browser to hang up, and the client hangs up as soon as it has one.
- Sessions panel re-fetches after an action instead of reusing a stale poll.

Closes #31
Closes #32
Closes #33
Closes #34
Closes #35

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

bin/devdesk

@@ -296,20 +296,24 @@ cmd_attach() {
     --list)
         [ $# -eq 1 ] || dd_die "--list takes no arguments"
         cmd_list
+        dd_linger
         return
         ;;
     --repo)
         shift
         cmd_repo "$@"
+        dd_linger
         return
         ;;
     --alerts)
         cmd_alerts
+        dd_linger
         return
         ;;
     --upload)
         shift
         cmd_upload "$@"
+        dd_linger
         return
         ;;
     --new | --rename | --end)
@@ -317,6 +321,7 @@ cmd_attach() {
         shift
         "cmd_$action" "$@"
         ok_json
+        dd_linger
         return
         ;;
     --existing)