This PR fixes a simple typo in the README.md file for the starter-cf-single example in the plugin-rsc package.

Change made:

• Fixed "deafult" → "default" in packages/plugin-rsc/examples/starter-cf-single/README.md

The typo was in the line describing the development environment:

- During development, SSR environment runs as Vite's deafult Node environment.
+ During development, SSR environment runs as Vite's default Node environment.

Verification:

• Searched all README.md files in the repository and confirmed this was the only instance of this typo
• Ran lint and format checks to ensure the change follows project standards
• Verified the fix is minimal and surgical (only one word changed)

This resolves the issue mentioned in the problem statement and ensures documentation accuracy.

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