Tag the colour-independent status that was already built and unrecorded

NFR-A11Y-3 — no status conveyed by hue alone — read as untagged, and
outstanding.md said "no compliance work found". Both were wrong. Five places
already implement it, and four of them name the requirement in a comment
explaining the design; what none of them had was a TRACES line.

- `histogram.rs::percentage` states clipping as a figure and keeps `<0.1%`
  distinct from `0%`, so the text cannot say "none" while the marker beside it
  is lit.
- `histogram.slint`'s ClipReadout is the other half: a marker that appears and
  disappears rather than changing tint, and the figure next to it. Either alone
  reads.
- `library.slint`'s star strip is a solid star against an outline, differing in
  shape and luminance, over an achromatic palette.
- `library.slint`'s FlagMark is a tick against a cross, and a reject also dims
  its whole cell.
- `peaking.slint`'s colour chips say "Red" and "Cyan". A control for choosing
  between hues, presented only as hues, is unusable by exactly the person most
  likely to need it.

The tag is honest about being wider than the evidence, and outstanding.md now
records both gaps. Only the clipping clause has a test that would fail if the
behaviour were removed; the three Slint components are argued rather than
asserted. And the requirement's first named example — catalog colour labels —
has no interface at all: `label` is a nullable column nothing writes or shows.
That clause is untestable rather than satisfied, and closes when the label UI
is built with a shape from the start.

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

docs/outstanding.md

@@ -260,9 +260,22 @@ on one control — the parameter slider in `adjust.slint` — and nothing is set
 all. Everything else in eighteen Slint files is unnamed to AT-SPI and TalkBack. The requirement's own
 caveat, that Slint's Android accessibility needs verifying, is spike S13, which has not run.
 
-**NFR-A11Y-3 — Colour-independent status.** No compliance work found. This is cheap to satisfy while
-a control is being written and expensive to retrofit across forty of them, which is an argument for
-doing it as part of the NFR-A11Y-2 pass rather than after it.
+**NFR-A11Y-3 — Colour-independent status.** Built where a control exists, and now tagged: the
+clipping readout pairs a marker that appears or disappears with a figure in words, the rating strip
+is a solid star against an outline in an achromatic palette, the pick/reject mark is a tick against
+a cross, and the focus-peaking colour chips say "Red" and "Cyan" rather than showing swatches. Each
+of those already carried the reasoning in a comment naming this requirement and simply had no
+`TRACES` line.
+
+Two caveats, because the tag now says more than the evidence does. **Only the clipping clause has a
+test** — `a_clipping_figure_distinguishes_none_from_nearly_none`, which pins `<0.1%` apart from `0%`
+so the figure cannot contradict the lit marker beside it. The three Slint components are
+inspected-and-argued, not asserted, and nothing would fail if a future edit made a star differ only
+in tint. **And the requirement's first named example has no interface at all**: catalog colour
+labels are a nullable `label INTEGER` column on the versions table and are set and shown nowhere, so
+the clause about them is untestable rather than satisfied. That clause closes when the label UI is
+built, not before, and it should be built with a shape from the outset — which is the same argument
+as below, for doing this alongside NFR-A11Y-2 rather than after it.
 
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