unify color palette, harden shikane service, misc sway/opencode updates

sway:
- config: re-apply shikane profile after every reload
  (exec_always shikanectl reload); restart waybar on reload
  (exec_always pkill+waybar); enable default_border pixel 2;
  add tlpctl power-saver at startup
- keybinds: disable floating_modifier (was "$mod normal") -
  experiment for windows popping out via accidental mod+click
- windows: case-insensitive pydm title match for floating rule
- swayfx + waybar style: unified 5-color palette (base00-0F) with
  doc headers; waybar theme restyled to match the sway palette
- waybar config: scratchpad module in left bar, "S{count}" format
- new quickshell shell.qml bar

systemd user units:
- shikane.service: bind to graphical-session/sway-session targets,
  Type=simple, Restart=on-failure (2s) with start limits so crashes
  recover without giving up permanently
- new sway-session.target and its wants/ symlinks

opencode:
- load AGENTS.md as instructions (new file)
- move OpenWebUI API key from hardcoded to {env:OPENWEBUI_API_KEY}

.config/systemd/user/shikane.service

@@ -1,10 +1,17 @@
 [Unit]
 Description=shikane
+PartOf=graphical-session.target
+After=graphical-session.target
+Requisite=graphical-session.target
+# Recover from crashes without giving up permanently
+StartLimitIntervalSec=60
+StartLimitBurst=10
 
 [Service]
+Type=simple
 ExecStart=/usr/bin/shikane
-Restart=always
-RestartSec=1
+Restart=on-failure
+RestartSec=2
 
 [Install]
-WantedBy=default.target
+WantedBy=sway-session.target

.config/systemd/user/sway-session.target

@@ -0,0 +1,6 @@
+[Unit]
+Description=sway compositor session
+Documentation=man:systemd.special(7)
+BindsTo=graphical-session.target
+Wants=graphical-session-pre.target
+After=graphical-session-pre.target