PR 1255: make the ignore rule dialog and the ignored checks clearer

The yellow is the warning banner's background, but the rows keep the greys picked for a plain row. The banner itself puts body text on it, not muted text. Both passes measured it, with the row colour composited over what is behind it:

All of it is 12-14px normal weight, so WCAG 1.4.3 asks for 4.5:1. The dashed ignored chips are disabled tags, which are exempt.

Ways out, for you or the designer: body text instead of muted text on those rows (what the banner does), a lighter tint, or the yellow on a narrower element than the whole row. Each changes the look, so I haven't picked one.

The new rule wins over the table's hover colour. On main every check row turns light grey under the pointer; on the PR the yellow rows stay yellow, so they are the only ones with no hover feedback. Pass B saw it from the computed colours; Pass A's probe measured the same background at rest and on hover.

Copilot's point holds. Open "+ N ignored" on a check, then widen its rule to cover every resource: the controller marks the check ignored as a whole and keeps each name's own flag, the row then lists all names and appends the ignored ones again, and the link that would close the list is gone. Vue also warns about duplicate keys.

Pass B dropped it, reading that this shape needs a second rule on the check. It doesn't: the dialog's default Create is "Selected resources" with every resource selected, and for such a rule the controller sets the check ignored once every resource is (ignore.go, "a check is ignored as a whole once every affected resource of it is ignored"). Pass A reproduced it in jest, Pass B in the browser by changing the store.

Copilot's other point. The list of ignored names checks every name against the list of reported ones, so its cost grows with the square of the names, and only while that check's list is open. Pass A: 79 ms at 2,000 names, 640 ms at 10,000, 4.2 s at 30,000 (drawing the chips included). Pass B: 0.36 ms at 1,000 for the filter alone. .105's checks have at most 5 names. It sits in the same function as 3, so it costs nothing extra to tidy while fixing that.

After picking 30 days the banner still says "To make any changes, set a new expiration", although that has just been done and "Will expire on ..." shows under the radios. I kept it because your note said the banner should always show; the issue only describes it when the dialog opens. Hiding it once a new expiration is picked is one line.

The banner makes the dialog taller, so at a 720px-high window Reason is cut off until you scroll inside the dialog. On main the same dialog fits. Layout only.

harvester/docs PR 1172 is still open and says "Entire check", "Ignore for", "+ 6 ignored", that the Show ignored label counts checks and resources, and that changing an expired rule without a duration shows a warning. Its dialog screenshot shows the old labels. It needs those lines and that image updated once this merges. PR 1225's Test Steps, which QA follows for issue 9747, also say "Entire check".