[brionmario]

Purpose

Combines #8, #9 and #10 into one pull request, one commit each, so they land together (thunder-id/thunderid#5904).

1. Bump vite in the self-care account sample to fix the launch-editor advisory (was Bump vite in the self-care account sample to fix the launch-editor advisory #10). A new high-severity advisory, launch-editor's fs.existsSync() existence check being bypassable on Windows, reaches self-care/account through its vite 8.0.16 devDependency. It fails pnpm audit --audit-level=high in the PR builder for every pull request. vite moves to 8.3.4, which is patched (>=8.1.6) and still accepted by @vitejs/plugin-react 6.0.2.
2. Add the Better Auth Next.js integration sample (was Add the Better Auth Next.js integration sample #9). Moves the sample from thunder-id/javascript-sdks to integrations/better-auth-nextjs.
   • Published package: it now depends on the published @thunderid/better-auth 0.1.1.
   • Standalone install: it has its own lockfile, plus the postcss override the Next.js quickstart carries.
   • README: links are absolute and setup includes pnpm install.
   • CI and release: the PR builder already discovers it, the release workflow gains a sample_better_auth_nextjs input, and the root README lists it.
3. Stop concurrent sample releases from failing on push races (was Stop concurrent sample releases from failing on push races #8). The first quickstart release (run 39429836038) failed for Express, Vue and Flutter: ten matrix jobs pushed their version bumps to main at once and gave up after five fixed-backoff attempts. Releases now run at most four at a time and retry up to ten times with a randomized wait.

Approach

See each commit. The second and third commits touch different parts of .github/workflows/release.yml. The combined workflow has 15 inputs, and its plan step was checked locally with the Better Auth and React samples selected.

Verified locally:

• self-care/account: pnpm audit --audit-level=high (2 low only), format:check, lint, build.
• integrations/better-auth-nextjs: pnpm install --frozen-lockfile, pnpm audit --audit-level=high (no known vulnerabilities), and pnpm build with and without a .env.

Related Issues

• Move the SDK quickstart samples to the thunder-id/samples repository thunderid#5904

Related PRs

• Supersedes Stop concurrent sample releases from failing on push races #8, Add the Better Auth Next.js integration sample #9, Bump vite in the self-care account sample to fix the launch-editor advisory #10
• Move the samples to the samples repository and add playgrounds javascript-sdks#126 (removes the Better Auth sample from the SDK repository)
• Point the docs at the samples repository and document the SDK playgrounds thunderid#5910 (repoints the docs)

Merge order: this PR before thunder-id/javascript-sdks#126 and thunder-id/thunderid#5910.

Checklist

• Followed the contribution guidelines.
• Manual test round performed and verified.
• Documentation provided. (Add links if there are any)
• Tests provided. (Add links if there are any)
  • Unit Tests
  • Integration Tests
• Breaking changes. (Fill if applicable)
  • Breaking changes section filled.
  • breaking change label added.

Security checks

• Followed secure coding standards.
• Confirmed that this PR doesn't commit any keys, passwords, tokens, usernames, or other secrets.