PNT1 2/8: border-radius, parsed as Chrome 145 and drawn natively on iOS and Android

[thejackshelton]

PNT1 part 2 of 8 (T115; notes/T046-paint-spec.md §5.2): border-radius and its four corner longhands. They are parsed and computed as Chrome 145 does, and Dragon draws them on iOS and Android with the translated paint-radius.ts from part 1.

Stacked on part 1. The base is review/pnt1-paint-engines, a copy of part 1's head. CI runs only for bases master and review/**. This PR shows only the radius commits, and the chain lands as a PNT1 train after trains 1–4.

What changed

• CSS.
  • The radius family (css/properties/radius.ts) and the border-radius shorthand (shorthands/radius.ts).
  • The paint value parser hook (css/paint-parsers.ts, called from stylesheet.ts), with Chrome's parsing checks.
  • Native checks in analysis/paint-values/radius.ts: rounded border styles Dragon does not draw are refused.
• Lowering and emitting:
  • The radius write, and a rounded border-box path from the translated engine (emit/paint/radius.ts, the roundedPath hook in native-support.ts).
  • The rounded background stage: a rounded box paints its colour itself, through the background module's runtime writer.
  • The rounded border stage, and the rounded overflow clip.
• Proof against Chrome:
  • Radius sample points (paint-samples/radius.ts), which keep base points off antialiased arcs.
  • The host paint model (parity/test/paint-model.ts), with pnt1-radius.test and pnt1-radius-edges.test.
  • Seven radius fixtures, two of them rejects.
  • The radius-square raster plant.
• State runtime. A border-radius write is refused by name; there is no state writer for it yet.

Changed tests (reasons)

• paint-seams, seams, grid and s4b tests: the radius module, longhands and shorthand are registered. The pinned lists and the longhand count gain them.
• device-run.test and device-lanes.test: the radius-square plant joins SUPPORT_PLANTS, PLANT_CASES and PLANT_RULES. The plant-verdict test uses its rule.
• state-program.test: border-radius is refused by name rather than dropped.
• native-backends.test: the background is now written through dragonBackground on both backends, because a rounded box paints its colour itself.
• p6a-dash-oracle.test: a rounded box is drawn by the rounded border painter, which the border stage tries before T116's side painter. The side-painter oracle therefore skips such a box. pnt1-radius.test compares those borders against Chrome.
• css-escapes.test: twins 13782 → 13795. The radius longhands and fixtures add 13 escaped twins, and each still reads as Chrome reads it.

What passed

• pnpm regen: fixed point after 3 passes (outputs in d779905), then 0 steps after the last source commit.
• pnpm typecheck: clean.
• pnpm test: 3667 passed, 12 failed, 1 skipped.
• Generated host sources: the Swift typechecks with swiftc for the iOS simulator, and the Kotlin compiles with kotlinc against android-36.

The 12 failing tests are the device-record checks (lanes.test, lanes-records.test, device-failures.test, p6a-promotion.test, lanes-concurrent.test). They fail only because the committed packages/parity/out/lanes.json is host-only: the device lanes run under the device lease at this branch's turn in the PNT1 train. No device run has been made for this branch.

🤖 Generated with Claude Code