ci: publish @base44/platform PR previews

[ozsay]

Summary

• New changes job picks the packages to preview: @base44/sdk on every PR (unchanged), @base44/platform only when the PR touches packages/platform/.
• publish-preview runs as a matrix over those packages and publishes @base44-preview/<package>@<version>-pr.<N>.<sha>. The name-mismatch safety checks and package.json restore are unchanged.
• One PR comment per package, found by a hidden <!-- package-preview:<package> --> marker, with install/alias commands for the right package (e.g. npm i "@base44/platform@npm:@base44-preview/platform@…"). The SDK keeps its existing header, so open PRs update their current comment instead of getting a second one. The comment lookup now reads 100 comments per page instead of 30.

Setup

• @base44-preview/platform exists on npm (placeholder 0.0.0).
• Before the first platform preview: add a trusted publisher on npmjs.com for @base44-preview/platform → repo base44/javascript-sdk, workflow preview-publish.yml.

Test plan

• YAML parses; check_wix_proxy_steps.py passes (file stays in the publish exemption).
• Selection logic simulated locally: this branch → ["sdk"], feat/platform-server-webhooks → ["sdk","platform"].
• This PR's own run publishes only the SDK preview and updates/creates the SDK comment.
• After merge, a push to feat(platform): add server entrypoint with createBase44PlatformServer #316/feat(platform): add webhooks module to the server entrypoint #319 publishes @base44-preview/platform and posts its own comment.

🤖 Generated with Claude Code

[github-actions]

🚀 Package Preview Available!

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Install this PR's preview build with npm:

npm i @base44-preview/sdk@0.8.53-pr.320.9f08a7a

Prefer not to change any import paths? Install using npm alias so your code still imports @base44/sdk:

npm i "@base44/sdk@npm:@base44-preview/sdk@0.8.53-pr.320.9f08a7a"

Or add it to your package.json dependencies:

{
  "dependencies": {
    "@base44/sdk": "npm:@base44-preview/sdk@0.8.53-pr.320.9f08a7a"
  }
}

• 📦 Preview Package: @base44-preview/sdk@0.8.53-pr.320.9f08a7a
• 🔗 View this commit on GitHub

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_{Preview published to npm registry — try new features instantly!}