Rebuild the primary blue ramp on an accessible 500 - #3376

#4199fd measured 2.92:1 on white, failing AA both as link text and as a
button fill behind white text — the same number either way, since contrast
is symmetric. Every admin link, primary button, active tab and settings
sidebar heading read at that ratio.

The ramp is rebuilt in OKLCh at one hue, lightness stepping evenly in
perceived terms and chroma peaking at 500, and now runs 25 to 900 like the
grey ramp beside it. 500 is #026ee8 at 4.77:1 and 700 #1256ae at 7.08:1;
500 is the lightest stop that clears 4.5:1, so it is the floor for text and
for anything sitting behind white text.

Values held outside the ramp came with it: three strays fold into tokens,
including an active-tab underline that sat at 2.89:1 against the 3:1 floor
for a state indicator, and the blue stops of gradients carrying white text
move up to clear 4.5:1 each. --blue-border folds into --primary-200.

Front-end and email defaults keep #4199FD — those paint customer forms, not
the admin, and are a separate decision. Third-party brand blues are
untouched.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

master's slider rewrite removed the block holding two of the three literals
this branch had moved onto tokens, and had already put the rest of the
component on --primary-500. Its version is taken whole, with the one
surviving literal converted. Build artifacts are regenerated from the
merged source rather than hand-resolved.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

The Forms list wraps its title in <strong>, the Entries list does not, so
the two lists resolved to different stops: 700 on Forms, 500 everywhere
else. 500 is the ramp's stop for links and 700 is where they go on hover.

The resting rule also outranked .frm_wrap a:hover on specificity, so a form
name had no hover feedback. The hover pair added here carries the extra
pseudo-class and wins.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>