feat(get_design_context): surface mixed-text segments + WRAP cross-axis spacing, omit no-op defaults

[awdr74100]

Three equal-or-better improvements to the highest-frequency read tool — the codegen grounding source of truth. Each is strictly faithful-or-smaller; no real design's generated code regresses.

What & why

• Mixed-style TEXT now carries segments — per-run characters + fontName + fontSize + fills (hex) + textDecoration + textCase. Previously a node with inline variation read as fontSize: "mixed" / textDecoration: "mixed" with no way to locate the bold word / underlined link / coloured span, so codegen flattened it to a single style (the classic "Terms and Privacy Policy with no underline" miss). The serializer already computed these (the long-proven get_node path) — full detail just dropped them; now it copies them with paints simplified to hex like everything else in this view. Zero extra compute at full detail.

• Auto-layout now captures WRAP cross-axis geometry — counterAxisSpacing (the gap between wrapped rows) and counterAxisAlignContent. A wrapping flex (tag cloud / chip group) kept its primary itemSpacing but lost the row gap entirely, forcing a guess. Emitted only when layoutWrap === 'WRAP' and non-default (Figma reports counterAxisSpacing: null under SPACE_BETWEEN, so it's omitted there).

• Omit no-op defaults consistently — absent visible = true, rotation = 0, opacity = 1, cornerRadius = 0. Strict equality (so a 0.99 opacity / 0.0001-rad rotation still surfaces; mixed corners are a symbol, never 0). Identical generated code, smaller payload; cornerRadius = 0 is the highest-volume of these — every frame/shape carries it.

A candidate to drop in-flow children's x/y was rejected: under WRAP it's currently the only row-gap signal, so it would regress — which is what surfaced the WRAP gap above.

Verification

• Full gate green: typecheck / lint / format:check / knip / build / test (693 tests), incl. new unit tests for all three (segments with hex fills, WRAP spacing across three cases, no-op omission).
• Live-verified on real designs: a genuine consent-label link (Bold + underline + coloured) recovered exactly via segments; no-op omission confirmed clean across several frames. WRAP is unit-test-only (no wrapping flex existed in the test designs, and the write tools can't synthesize a non-zero counterAxisSpacing).

Files

shared/serialized-node.ts (WRAP schema), shared/design-context.ts (segments type + schema), shared/design-context-dedupe.ts (export simplifyPaint), plugin/serializer.ts (WRAP emit), plugin/handlers/get-design-context.ts (segments copy + no-op omission), tests, and skills/figma-codegen/references/grounding.md (how to read segments + WRAP row gap).