feat(vite-dev-server): migrate to async fs operations for better perf…

[lucgonp]

…ormance

• Replace fs.readFileSync with async fs.readFile
• Add proper error handling with debug logs
• Improve performance by avoiding event loop blocking
• Remove TODO comment about async fs methods

This follows Node.js best practices and improves DX with faster build times.

• Closes

Additional details

Steps to test

How has the user experience changed?

PR Tasks

• Have tests been added/updated?
• Has a PR for user-facing changes been opened in cypress-documentation?
• Have API changes been updated in the type definitions?

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Note

Switches to fs/promises, asynchronously loads/caches the init script with error handling, and updates index.html reading to async.

• Vite dev server plugin (npm/vite-dev-server/src/plugins/cypress.ts):
  • Replace sync fs.readFileSync with async fs.readFile via fs/promises; update index.html reading to fs.readFile.
  • Add loadInitFile with debug logging and robust error handling; introduce cached loaderPromise with reset on failure.
  • transformIndexHtml: await cached loader content and inject it into the generated HTML.

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[AtofStryker]

@lucgonp Do you have any performance benchmarks to share to show the improved performance here? I feel like there needs to be a tangible benefit here to measure given the increase in code complexity.

Is there a reason we need to have the promise be a singleton. I'm guessing there is some type of race condition when loading the file?