Prepare WeBaseUI 1.0 RC

[xuewill]

What changed

• mature all 28 public Svelte components with shared API contracts, tokens, overlay/focus infrastructure, localization, RTL, forced-colors, reduced-motion, and target-size behavior
• rebuild the documentation experience with complete component references, search, accessible specimens, brand assets, and Lucide-only design checks
• add unit, SSR, browser, accessibility, visual regression, consumer compatibility, package-size, token, support-policy, and changeset quality gates
• add release governance, Changesets stable/next/canary workflows, npm OIDC trusted publishing, provenance-aware registry smoke checks, and the release runbook
• add RC readiness, screen-reader audit, adoption, performance, support, security, CODEOWNERS, and issue/PR templates

Why

This completes the repository maturity roadmap needed to prepare the packages for a 1.0 release-candidate cycle. It turns previously implicit component behavior and release expectations into tested contracts and repeatable automation.

Impact

• @webaseui/core and @webaseui/svelte receive minor-version changes through the included changesets
• consumers get stronger accessibility, browser consistency, theming, localization, and documented API guarantees
• maintainers get CI-enforced compatibility and a tokenless npm release path with SLSA provenance

Validation

• npm run check (76 unit tests; 99.61% statements, 99.09% branches, 100% functions and lines; all typechecks and policy gates passed)
• npm run check:consumer (minimum and current supported Svelte/TypeScript toolchains)
• npm run test:browser (84/84 across Chromium, Firefox, and WebKit)
• npm run test:visual (47/47 on macOS Chromium baselines)
• npm run check:changeset
• npm audit --audit-level=high (0 vulnerabilities)
• git diff --check

Remaining RC sign-off

• complete the manual VoiceOver/Safari and NVDA/Firefox-or-Chrome audit records before declaring the candidate RC-ready
• after this workflow is on main, verify the next channel publish and npm provenance attestations