feat: dashboard-only mode and keystone settings integration

The second display is now optional: [display] enabled = false skips the
headless output, wayvnc, AVNC and the VNC tunnel, so the tablet runs the
dashboard alone. `deck-it env` reports it as EXTEND.

Keystone's new deck-it page (quickshell, desktop/modules/deckit) edits
the config and the autostart line, which needed:

- The user config is merged over the shipped config.toml key by key
  within each table instead of replacing it whole, so the page writes a
  sparse file and an unset key falls back to the default.
- `deck-it defaults` prints the shipped config as JSON for the page's
  placeholders, so keystone never copies the defaults.
- `deck-it status` prints one JSON line (server, display, waiting,
  tablet, extend) for the page's status line and restart check.
- [launch] is now `apps`, a list of desktop ids run with gtk-launch,
  with name and icon read from the .desktop file, so the page can pick
  launchers from the installed apps. The old command tables are gone;
  the client still sends only an id, which must be listed and installed.
  A launcher whose icon the theme lacks shows its name.
- [wifi] address gives the tablet's address in config. The last address
  that worked is kept in ~/.config/deck-it/last-wifi: `stop` deletes the
  runtime serial file, so a restart from the page used to wait forever.
- `stop` also ends a login's `wifi --wait`, matched by its own command
  line only, so repeated restarts do not pile up waiters.

Also fixed: `deck-it env` fell through into the usage text, and the
usage text printed the license header since the header was added.

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

1 files changed, 13 insertions, 2 deletions

diff --git a/AGENTS.md b/AGENTS.md
index c25dd1f..e1d804e 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -33,8 +33,19 @@ Keep the server dependency-free apart from that one package.
   monitor for `position = "auto-below"`, and paints it with the first monitor's
   swaybg image.
 - The launcher (`deck-it`) handles USB and Wi-Fi (`pair`/`wifi`), the tunnels,
-  wayvnc and AVNC. `adb mdns` may be unsupported; `deck-it wifi <ip:port>` takes
-  an explicit address.
+  wayvnc and AVNC. `adb mdns` may be unsupported; `deck-it wifi <ip:port>` or
+  `[wifi] address` gives an explicit one; otherwise the last address that
+  worked (`~/.config/deck-it/last-wifi`, kept across `stop` and reboots).
+  `[display] enabled = false` skips the headless output, wayvnc and AVNC.
+  `deck-it status` prints one JSON line for keystone's page; keep its keys.
+- Config: `deckit/config.py` merges `~/.config/deck-it/config.toml` over the
+  shipped `config.toml` per key within each table (a list is replaced whole).
+  Keystone's deck-it page (quickshell repo, `desktop/modules/deckit`) writes
+  that sparse file and reads the defaults from `deck-it defaults`; keep that
+  JSON shape stable.
+- Launchers are `[launch] apps`, desktop ids run with `gtk-launch`; label and
+  icon come from the `.desktop` file. The client sends the id, which must be
+  configured and installed.
 
 ## Conventions