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>

tests/attach.bats

@@ -327,6 +327,23 @@ posts() { [ -f "$TMP/posts" ] && wc -l <"$TMP/posts" || echo 0; }
     kill "$RECEIVER"
 }
 
+@test "under ttyd, one-shot replies wait for the browser to hang up (#35)" {
+    start_server
+    # No tty (CLI, tests): no waiting.
+    start=$(date +%s%N)
+    DEVDESK_VIA_TTYD=1 DEVDESK_LINGER=2 devdesk attach --list >/dev/null
+    [ $(( ($(date +%s%N) - start) / 1000000 )) -lt 1500 ]
+    # On a tty, as under ttyd: the reply is printed, then it waits.
+    start=$(date +%s%N)
+    run script -qec "DEVDESK_VIA_TTYD=1 DEVDESK_LINGER=0.6 '$REPO/bin/devdesk' attach --list" /dev/null
+    elapsed=$(( ($(date +%s%N) - start) / 1000000 ))
+    [[ $output == *'"sessions"'* ]]
+    [ "$elapsed" -ge 500 ]
+    # Errors are printed before the wait, too.
+    run script -qec "DEVDESK_VIA_TTYD=1 DEVDESK_LINGER=0.3 '$REPO/bin/devdesk' attach --rename nosuch x" /dev/null
+    [[ $output == *"no session named"* ]]
+}
+
 @test "alerts reports unconfigured and unreachable Grafana cleanly" {
     run env DEVDESK_GRAFANA_URL= devdesk alerts
     [ "$status" -eq 0 ]