Screenshots: Fn+p on every screen (#83)

Fn+p saves the screen as it is to /screenshots, as the Shell's `screenshot`
does, from anywhere: text fields, dialogs and the help panel included. The
key never reaches an App.

It refuses on Settings > Debug Console, which shows the token: a picture of
that page is a copy of the token in a file (App::showsSecret). `key shot`
presses it over the consoles.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EhqxQ49eCju4CzKYNjZzwT

site/data/keys.toml

@@ -9,6 +9,7 @@ rows = [
     ["Fn `", "home, the Launcher"],
     ["; . , /", "arrows (Fn+ while typing)"],
     ["Fn h  ?", "these keys (? not typing)"],
+    ["Fn p", "a screenshot, on the card"],
 ]
 
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