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, 29 insertions, 3 deletions

diff --git a/deckit/config.py b/deckit/config.py
index aac5ad9..e20bc00 100644
--- a/deckit/config.py
+++ b/deckit/config.py
@@ -24,6 +24,8 @@ from pathlib import Path
 
 ROOT = Path(__file__).resolve().parent.parent
 MONITOR_NAME = re.compile(r"[A-Za-z0-9_-]{1,32}")
+WIFI_ADDR = re.compile(r"[A-Za-z0-9.-]{1,253}:[0-9]{1,5}")
+DESKTOP_ID = re.compile(r"[A-Za-z0-9._-]{1,255}")
 
 
 def user_config_path() -> Path:
@@ -34,6 +36,8 @@ def config_error(cfg: dict) -> str | None:
     d, ports = cfg.get("display", {}), cfg.get("ports", {})
     if not MONITOR_NAME.fullmatch(str(d.get("name", "TAB"))):
         return "display.name must be letters, digits, - or _"
+    if not isinstance(d.get("enabled", True), bool):
+        return "display.enabled must be true or false"
     refresh = d.get("refresh", 60)
     if not isinstance(refresh, int) or not 1 <= refresh <= 240:
         return "display.refresh must be a number from 1 to 240"
@@ -44,13 +48,35 @@ def config_error(cfg: dict) -> str | None:
                 return f"ports.{key} must be a number from 1024 to 65535"
     if ports.get("command_center", 8765) == ports.get("display", 5900):
         return "ports.command_center and ports.display must differ"
+    addr = cfg.get("wifi", {}).get("address", "")
+    if addr and not (isinstance(addr, str) and WIFI_ADDR.fullmatch(addr)):
+        return "wifi.address must be host:port, like 192.0.2.10:37099"
+    apps = cfg.get("launch", {}).get("apps", [])
+    if not isinstance(apps, list) or not all(isinstance(a, str) and DESKTOP_ID.fullmatch(a) for a in apps):
+        return "launch.apps must be a list of desktop ids, like \"kitty\""
     return None
 
 
+def merge(base: dict, over: dict) -> dict:
+    """The user's file over the defaults, key by key within each table."""
+    out = dict(base)
+    for key, value in over.items():
+        both = isinstance(value, dict) and isinstance(base.get(key), dict)
+        out[key] = {**base[key], **value} if both else value
+    return out
+
+
+def defaults() -> dict:
+    with open(ROOT / "config.toml", "rb") as f:
+        return tomllib.load(f)
+
+
 def load_config() -> dict:
-    path = user_config_path() if user_config_path().is_file() else ROOT / "config.toml"
-    with open(path, "rb") as f:
-        cfg = tomllib.load(f)
+    cfg, path = defaults(), ROOT / "config.toml"
+    if user_config_path().is_file():
+        path = user_config_path()
+        with open(path, "rb") as f:
+            cfg = merge(cfg, tomllib.load(f))
     if err := config_error(cfg):
         sys.exit(f"{path}: {err}")
     return cfg