feat(accent): light IKEA TRADFRI colour bulbs in the accent

udt-bulb fades every paired colour bulb to the wallpaper accent through
the TRADFRI gateway's local CoAP API, over DTLS-PSK via libcoap's
coap-client. --pair trades the gateway's security code for an identity
of its own and records the colour bulbs in ~/.config/udt/tradfri.json.

Takes udt-ledstrip's on and off. A bare run, as udt-accent starts it,
skips bulbs that are off, since the gateway switches a bulb on for any
colour change. Colour and brightness go in separate requests, colour
first: combined, or with a colour sent during a brightness fade, the
gateway drops part of it.

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

1 files changed, 15 insertions, 1 deletions

diff --git a/AGENTS.md b/AGENTS.md
index 4c3ccae..5a31dee 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -242,6 +242,20 @@ hypridle's idle timeout, for the same reason as `off`: NetworkManager drops the
 network on the same sleep signal hypridle's `before_sleep_cmd` answers. That
 `before_sleep_cmd` sends it too, as a best effort for any other suspend path.
 
+`udt-bulb` does the same for IKEA TRADFRI colour bulbs, called beside every
+`udt-ledstrip`, except that suspend switches the bulbs off: the breathing
+strip alone says the desktop is asleep. A bulb shows one colour, so it gets
+the accent alone. The bulbs are Zigbee, reached through the
+TRADFRI gateway's local CoAP API over DTLS-PSK, which Python cannot speak, so
+it calls libcoap's `coap-client` (SBo `libcoap`). `udt-bulb --pair HOST CODE`
+trades the code on the gateway's label for an identity of its own and writes
+`~/.config/udt/tradfri.json` with every colour bulb listed; trimming that list
+by hand picks which bulbs follow. Two gateway quirks shape the requests,
+both found on the real bulb: any colour change switches a bulb on, so a bare
+run reads the state first and skips an off bulb; and a request setting colour
+and brightness together, or a colour sent while a brightness fade runs, is
+partly dropped, so colour goes first and brightness after, separately.
+
 **Sublime's, GRUB's and the homepage's accents are replaced, not substituted
 into a placeholder.** GRUB and the homepage are generated by udt-palette with
 the scheme's accent, then rewritten in place, before `udt-grub` and
@@ -305,7 +319,7 @@ profile, and the new tab stays blank.
 
 Not everything tracks the wallpaper. rofi, quickshell, Hyprland borders,
 hyprlock's border (through `~/.cache/udt/hyprlock-border.conf`), Sublime's
-colour scheme, Firefox, GRUB, the homepage, the AK820 Pro keyboard and the LED strip do; conky, Qt, GTK, waybar, hyprlock's panel palette
+colour scheme, Firefox, GRUB, the homepage, the AK820 Pro keyboard, the LED strip and the TRADFRI bulbs do; conky, Qt, GTK, waybar, hyprlock's panel palette
 (from `templates/hyprlock/hyprlock-palette.conf`) and Sublime's UI chrome sit
 on the scheme's accent, lavender by default, which is also the fallback
 when a wallpaper is too grey to snap. Qt and GTK apps only reread a theme on restart,