fix(runtime): support CSS v-bind() on Lynx native

[Huxpro]

Supersedes #144

This is the writable, rebased continuation of #144. It preserves the full intended CSS v-bind() behavior while rebasing the PR commits onto current main (4e75e3e). The original cross-fork head is read-only to the maintainer account, so it could not be updated in place.

Original #144 head: b8256b2
Rebased head: bc9d5b4

Summary

• Adds Background-Thread-safe support for v-bind() in Vue style blocks on Lynx native.
• Writes CSS custom properties onto component root element(s) through the ops pipeline.
• Relies on the Lynx engine propagation fix from [BugFix] Fix CSS custom property propagation in FiberSetInlineStyles lynx-family/lynx#5912; no descendant-stamping workaround remains.
• Updates the CSS features example and EN/ZH compatibility docs.
• Adds focused BG-runtime regression coverage for mount, reactive updates, fragments, v-show, style-only updates, and root-only stamping.
• Requires Lynx engine >= 3.9.0 and enableCSSInlineVariables: true; enableCSSInheritance is not required.

Rebase/conflict resolution

• Kept current main's scoped-CSS support and newer runtime/test infrastructure.
• Kept fix(runtime): support CSS v-bind() on Lynx native #144's final root-only CSS-variable contract and 3.9.0 compatibility wording instead of reviving its earlier O(N) descendant workaround.
• Dropped the already-upstream entry.ts encode-data fix from this diff.
• Removed a duplicate useCssVars export exposed by replaying the old commits over current main.

Verification

• packages/upstream-tests: ./node_modules/.bin/vitest run --config vitest.local.config.ts src/use-css-vars.spec.ts — 12/12 passed.
• packages/upstream-tests: ./node_modules/.bin/vitest run --config vitest.local.config.ts — 50/50 passed.
• examples/css-features: ./node_modules/.bin/rspeedy build — web and Lynx bundles built.
• ./node_modules/.bin/biome check . — passed (108 files on final base).
• pnpm changeset status --since=4e75e3ef1efc17a239adaa48a665ef699a6423f5 — passed.
• pnpm run build: internal/runtime/main-thread/plugin built locally; the final unrelated types declaration step was blocked by a missing local vue type link. The clean GitHub Build check passed on the final head.
• GitHub CI: Build, Changeset Check, Lint, Test - Pipeline, Test - Vue Upstream, and Test - Dev Smoke all passed.
• Vercel and Vercel Preview Comments passed.

External gates

None remaining. Native descendant-cascade behavior was previously verified on LynxExplorer 3.9.0 with enableCSSInlineVariables: true and enableCSSInheritance: false; local unit tests intentionally cover only BG op emission.

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Project	Deployment	Actions	Updated (UTC)
vue-lynx	Ready	Preview	Aug 17, 2026 8:16pm