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>

libexec/devdesk-lib.sh

@@ -43,8 +43,19 @@ DEVDESK_CONTEXT_DIR="$DEVDESK_STATE_DIR/context"
 DEVDESK_STATUS_DIR="$DEVDESK_STATE_DIR/state"
 DEVDESK_NAME_RE='^[A-Za-z0-9][A-Za-z0-9_-]{0,63}$'
 
+# Under ttyd, a command that exits right after printing sometimes loses its last
+# output: ttyd sees the exit and closes the WebSocket before reading the pty
+# (devdesk#35). One-shot replies and errors therefore wait, at most
+# DEVDESK_LINGER seconds, for the browser to hang up once it has the answer
+# (ttyd then sends SIGHUP). devdesk-serve sets DEVDESK_VIA_TTYD=1.
+dd_linger() {
+    [ "${DEVDESK_VIA_TTYD:-}" = 1 ] && [ -t 0 ] || return 0
+    read -r -t "${DEVDESK_LINGER:-1}" _ 2>/dev/null || true
+}
+
 dd_die() {
     printf 'devdesk: %s\n' "$*" >&2
+    dd_linger
     exit 1
 }