fix(theme): lift game hues that are unreadable on the dark ground

readableHue returned every dark hue untouched on the claim that all of
them already cleared 4.5:1 there. Five did not, and Fate's navy was
1.8:1, so its name under the headline deadline was nearly invisible.
Those five are now lifted in lightness only, keeping hue and saturation;
the fifteen that pass are unchanged. The owner approved relaxing the
"dark theme does not move" rule to this, and AGENTS.md and PRD F15 say so.

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

docs/PRD.md

@@ -492,7 +492,9 @@ wrong:
 - **A game keeps its colour.** The hues are identity (F1) and were all picked against a near-black
   ground; on paper the bright ones vanish. They are darkened until they read, along the same hue, so
   Wuthering Waves is still the green one — including the hues a reader picked for a game they
-  invented (F13).
+  invented (F13). The same bar holds on dark: five hues were too dim for the ground they were
+  picked against (Fate's navy at 1.8:1), so those alone are lifted in lightness until they clear
+  4.5:1, and every hue that already read is left exactly as it shipped.
 
 Switching is instant, costs nothing and saves nothing: no reload, and nothing marked, typed or
 ticked is touched. And it survives the load it is chosen on — the shell sets the theme before first