Fix the contrast the audit could finally measure

Contrast is the one check I've got wrong twice, both times by being clever about
backgrounds. The first version read only background-color, so text on any of the
gradient-painted sheets was measured against transparency and the dealer puck's
dark "D" was reported at 1.2:1 against nothing. The second over-corrected and
treated low-alpha gradient stops as opaque, scoring white-on-dark at 1.0:1.

So this one is built to be incapable of false positives rather than exact.
Backgrounds composite through alpha; where a gradient is involved every colour stop
is tried and the most flattering one used. A finding means the text fails even
under the reading most generous to it.

It's checked against known answers before being believed: black on white at 21:1,
white on white at 1:1, #767676 on white at the 4.54:1 AA boundary, white over a
dark gradient, dark text on that same gradient, white over a 6% white wash on a
near-black page. Nine cases, all correct — and building them found a real bug in
the check, which walked past an opaque gradient and offered the page background as
a candidate. That made it too lenient, which is as bad as the old false positives.

What it found:

Both blind badges failed against their own gradients, in 9px bold text a dealer
reads at a glance across a table. At the worst stop: small blind 3.52:1, big blind
2.15:1. The small blind keeps its blue and darkens to 4.77:1. The big blind flips
to dark text on brighter gold, 5.84:1 — how a gold chip is marked anyway, and it
makes the two badges far easier to tell apart at speed.

Quick Split's footnote names a control the dealer is told to reach for, and that
name inherited the muted grey of the surrounding aside: 3.39:1. Emphasised text
carrying an instruction gets its own colour now.

The felt watermark came back at 1.19:1 and is meant to. It's decoration; holding it
to a reading threshold would mean making it not a watermark. It's aria-hidden now,
which says the same thing where it also does some good, and the audit skips
aria-hidden subtrees.

32 contrast passes over the table, all five overlays and Quick Split at five
viewports: zero findings, zero unmeasured. Layout audit still clean. 137 tests pass.

Co-Authored-By: Claude Opus 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_015bnp7xKUPFFSpwkYNFaPgb

JoshHeaps.Net/wwwroot/css/casino/quicksplit.css

@@ -516,6 +516,15 @@ button,
     text-align: center;
 }
 
+/* This footnote names a control the dealer is being told to reach for, so the name
+   itself has to be readable — it was 3.39:1 at its worst, inheriting the muted grey
+   the surrounding sentence is deliberately set in. Emphasised text carrying the
+   instruction gets its own colour rather than the aside's. */
+.splitFootnote strong {
+    color: #a8a8a8;
+    font-weight: 600;
+}
+
 .splitFootnote a {
     color: #a9782f;
 }