Follow the active theme in T3 Code

T3 Code reads themes an environment publishes into its state directory, so
a generated t3code.json carries the palette the same way claude.json and
vscode-theme.json already do, and omarchy-theme-set-t3code republishes it
on every theme change for the app to pick up live.

The template overrides only the roles a theme actually designs -- terminal
and code surfaces, text on canvas, borders, selection -- and leaves muted
text, placeholders, and status foregrounds to T3 Code, which contrast-solves
them against whatever canvas it is given. Overriding those directly cost
readability on light themes: White fell to 1.0:1 on placeholder text.

Installing from the menu now routes through omarchy-install-ai-t3-code so a
fresh install publishes the current palette and opens wearing it.

bin/omarchy-theme-set

@@ -372,6 +372,7 @@ post_theme_commands=(
   omarchy-theme-set-pi
   omarchy-theme-set-claude
   omarchy-theme-set-hermes
+  omarchy-theme-set-t3code
   omarchy-theme-set-browser
   omarchy-theme-set-vscode
   omarchy-theme-set-obsidian