fix(#462): text dimmed to 70% or below fails AAA on every surface — remove it, then guard it

[TortoiseWolfe]

text-base-content at 70% opacity or below fails the 7:1 AAA gate on every surface in the
light theme. #411 measured that and removed it. It came back, and nothing noticed for months.

Full finding in #462, which is rewritten around what remains rather than what this fixes.

Why nothing noticed

#459: axe-core returns a pass with contrastRatio: null on these nodes, so
color-contrast.spec.ts — which asserts on violations — has been green on them the whole
time. A removal without a guard is a removal that gets undone, and that is exactly what
happened between #411 and today.

The measurement (#462, canvas readback — getComputedStyle returns oklch() unparsed)

scripthammer-light, gate 7:1:

	/100	/85	/80	/70
on base-100	12.96	8.30	7.08	5.20
on base-200	11.73	7.73	6.62	4.98
on base-300	10.10	6.88	6.05	4.57

/70 and below fails everywhere, with no judgement call about which surface the text landed
on. That is what this removes.

The instances were worse than the table

All eight real ones sat in src/twin/cesium/ on bg-base-100/90 with backdrop-blur,
floating over the Cesium canvas at 10–11px. The table assumes opaque surfaces, so a
translucent panel over an arbitrary 3D scene is unbounded-worse than its worst row — the #715
situation, where the answer was solid text on a raised surface.

Replaced with solid text-base-content. The de-emphasis survives: these are already 10–11px
beside 13px+ labels, and size costs no contrast.

Verified the symptom first

The five instances #462 originally named are all already clean — MessagingGate,
MessageThread, messages/new-group, messages/setup. The issue as written did not
reproduce. The real finding was elsewhere, which is why #462 is rewritten rather than closed.

Why this is Refs and not Closes

184 /80 and /85 remain, across ~100 files, and they cannot be swept mechanically —
/80 passes on base-100 (7.08, a margin of 0.08) and fails on base-200 (6.62). That
needs a per-call-site surface determination and is its own piece of work.

The guard

scripts/__tests__/text-opacity-aaa-floor.test.js, in pnpm test:scripts and therefore inside
the required Test (20.x) check.

It exempts genuinely decorative content, because WCAG does — aria-hidden="true", or
<Icon … decorative /> which Icon.tsx:61 turns into aria-hidden. It does not accept a
comment claiming decorativeness: docs/page.tsx carries exactly such a comment, and it is the
prop six lines below that actually hides the glyph. Accepting prose would let a stale comment
exempt live markup.

globals.css is allowlisted with its reason (code-block line numbers, select-none) and
flagged in #462 as arguably informational rather than decorative — recorded, not silently
skipped.

Mutation-verified, mutant confirmed in the file first: restoring /60 at BuildingCard.tsx:151
fails the guard naming that exact file:line. Controls prove the detector fails in both
directions, that an aria-hidden 20 lines away does not exempt, and that prose containing
the word "decorative" does not either.

One process note worth keeping

The first sed for this change silently did nothing — | delimiter against \|
alternation, the exact trap CLAUDE.md documents. It was caught only by comparing before/after
counts (6 -> 6), which is why that comparison is in the workflow rather than trust.

Verified

type-check clean · lint clean · component tests 33 passed · pnpm test:scripts 363 passed

Refs #462, #411, #459, #715