palette: enlarge the region title into WCAG large class; repoint the grabbed envelope handle off hue

Corrects theme.h's large-text thresholds, names accent/secondary's real
binding limiter, and adds compositeOver so the loop-span fill's 2.25:1
under-floor pair is asserted rather than assumed.

src/shell/panel/panel_render.cpp

@@ -327,12 +327,14 @@ void drawRegionHeader(LICE_IBitmap* bmp, const RECT& region, const char* title,
     // Title, left. The two regions are distinct KINDS of container, so the title carries a
     // CATEGORICAL accent (secondary/tertiary mark kinds, never intensity) — Pool = secondary
     // teal, Banks = tertiary purple. This is a category mark, NOT the "what's live" signal
-    // (that stays the primary-lime "Active:" readout beside it).
+    // (that stays the primary-lime "Active:" readout beside it). Font::RegionTitle, not
+    // Font::Title: an accent this deep only clears the 3:1 indicator floor, so the type has to
+    // be large enough to be ENTITLED to it — see draw_kit.cpp's metrics static_assert.
     RECT titleRc = hdr;
     titleRc.left += 8;
     titleRc.right = titleRc.left + 120;
     const Role titleRole = poolBtnIsPool ? Role::AccentSecondary : Role::AccentTertiary;
-    kitText(bmp, toKitBox(titleRc), title, Font::Title, titleRole, Align::Left);
+    kitText(bmp, toKitBox(titleRc), title, Font::RegionTitle, titleRole, Align::Left);
 
     // Active-bank readout — the UNMISTAKABLE indicator, in the PRIMARY accent role in BOTH
     // region headers so the active/capture-target bank is legible even when it is not the