whatsthat: layout pass reclaiming desktop/mobile space (#705, #707, #710, #711)

[WilfordGrimley]

Summary

• Pins the reference card (Subject) inside the hero container via position: sticky
  (not the viewport) so it stays visible while scrolling at every width, including the
  compacted horizontal strip on narrow containers.
• Raises WtcHero/WtcHead's own max-width from 1180px to 1600px and passes fullWidth
  to whatsthat.tsx's ProjectContainer - the sitewide 1200px content cap, not the
  hero's own value, was the actual constraint keeping desktop narrow.
• Shows the attribute-chip filter panel automatically for identify_printing/
  confirm_suggestion questions instead of behind a manual toggle, and moves it out of
  a ring-around-the-card composition into the questions column, so it can no longer
  share a box with (and therefore can't occlude) the pinned reference card.
• Collapses an implied-negative chip's label instead of only dimming it, reclaiming the
  row space several dimmed siblings used to reserve.
• Lets SuggestedThumb/CandidateButton release their resting overflow: hidden clip
  for exactly the hover duration their zoomed thumbnail needs to escape it, so hover-zoom
  is no longer cut flush at the tile edge.
• Drops the oversized .big modifier from the Level 1 Yes button so it reads at the same
  size as its sibling answer buttons.

Test plan

• npm test (Jest) - 73 suites / 676 tests passing
• npx playwright test - 351 tests total, 344 passed, 6 skipped, 1 flaked under
  parallel load in an unrelated file (SelectVersionSection.spec.ts), confirmed
  passing standalone
• npm run build - compiles clean, no type errors
• .github/scripts/coverage_delta.py --base origin/master - clean (2 acked renames,
  both recorded in .github/coverage-acks.txt)
• Manual verification in a real Chromium browser at phone (390px), tablet (800px),
  and desktop (1600px) widths: reference card stays visible while scrolling, the
  chip panel never overlaps it, desktop uses its available width, hover-zoom is no
  longer clipped, and the Level 1 answer row reads as a hierarchy