Only offer Update > Extra Themes when there is one (#7775)

* Only offer Update > Extra Themes when there is one

omarchy-theme-update pulls the themes under ~/.config/omarchy/themes that came from a git clone, so on a machine that has never installed one by hand the row opens a terminal that prints nothing and closes. Guard it with the same predicates the command itself applies, since a row that shows over a symlinked theme or a worktree's `.git` file is the same dead end in a narrower shape, and pin the two to each other in the guard test.

Co-Authored-By: Codex XHigh <noreply@openai.com>

* Extract the Extra Themes guard into omarchy-theme-extras

The row's `when:` and omarchy-theme-update each carried their own idea of which themes came from a git clone, and the two only matched because a test held them together. Name it once instead: omarchy-theme-extras lists those directories and exits nonzero when there are none, so the row asks exactly the command its action runs. Living in a script also puts the glob out of reach of whatever shopt a login shell left set for the guard batch.

Co-Authored-By: Codex XHigh <noreply@openai.com>

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Co-authored-by: Codex XHigh <noreply@openai.com>
(cherry picked from commit 13a969e1ab)

default/omarchy/omarchy-menu.jsonc

@@ -326,7 +326,7 @@
   "update.omarchy": {"icon":"","iconFont":"omarchy","label":"Omarchy","action":"omarchy-launch-floating-terminal-with-presentation omarchy-update"},
   "update.channel": {"icon":"󰔫","label":"Channel"},
   "update.config": {"icon":"","label":"Config","title":"Reset to default"},
-  "update.themes": {"icon":"󰸌","label":"Extra Themes","action":"omarchy-launch-floating-terminal-with-presentation omarchy-theme-update"},
+  "update.themes": {"icon":"󰸌","label":"Extra Themes","when":"omarchy-theme-extras","action":"omarchy-launch-floating-terminal-with-presentation omarchy-theme-update"},
   "update.process": {"icon":"","label":"Process","title":"Restart"},
   "update.hardware": {"icon":"󰇅","label":"Hardware","title":"Restart"},
   "update.firmware": {"icon":"","label":"Firmware","action":"omarchy-launch-floating-terminal-with-presentation omarchy-update-firmware"},