docs: fix frontend build sequence and add Windows compatibility note

[TanXudong-Vivo]

Description

This PR fixes a logical error in the "Running the Restaurant Finder demo" section of the README.

What changed

• Reordered the frontend build steps so that renderers/web_core is built before renderers/markdown/markdown-it
• Added a troubleshooting note for Windows users about manually installing @rollup/rollup-win32-x64-msvc if needed

Why

@a2ui/markdown-it depends on @a2ui/web_core. In the current README order, building markdown-it first can result in:

TS2307: Cannot find module '@a2ui/web_core'

Additionally, on Windows environments, npm install may fail to install Rollup's optional native dependency, which can cause the npm run dev step to fail unless @rollup/rollup-win32-x64-msvc is installed manually.

Verification

Verified on a clean Windows environment:

• Before: building markdown-it first failed with TypeScript errors
• After: following the new sequence (web_core -> markdown-it -> lit -> shell) completed successfully
• The Vite dev server started successfully at http://localhost:5173/

Closes #1168

Pre-launch Checklist

• I signed the [CLA].
• I read the [Contributors Guide].
• I read the [Style Guide].
• I have added updates to the [CHANGELOG].
• I updated/added relevant documentation.
• My code changes (if any) have tests.

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[gemini-code-assist]

Code Review

This pull request updates the README.md to reorder and number the build steps for the samples, ensuring the Web Core library is built first. It also adds a troubleshooting note for Windows users regarding the @rollup/rollup-win32-x64-msvc module. I have no feedback to provide.