fix: use consistent CSS precedence for dynamic imports

[TrevorBurnham]

This PR fixes CSS ordering inconsistencies in the App Router by ensuring that CSS from dynamic imports (next/dynamic) uses the same precedence values as CSS from static imports.

Fixes #42082

Problem

When using next/dynamic in the App Router, CSS files were being loaded with different React precedence attributes depending on how they were imported:

• Static imports: Used precedence="next" (production) or precedence="next_<path>" (development)
• Dynamic imports: Used precedence="dynamic"

This inconsistency caused unpredictable CSS ordering, particularly when the same stylesheet was referenced through both static and dynamic import paths.

React's resource deduplication relies on matching href attributes to prevent duplicate stylesheets, but different precedence values could lead to inconsistent ordering behavior.

Solution

Modified PreloadChunks component in preload-chunks.tsx to use the same precedence pattern as renderCssResource:

// Before
precedence="dynamic"

// After
const precedence = process.env.NODE_ENV === 'development' ? 'next_' + chunk : 'next'

This ensures:

• Production: All CSS uses precedence="next"
• Development: All CSS uses precedence="next_" for proper HMR ordering
• Consistency: Same precedence regardless of import method

[ijjk]

Allow CI Workflow Run

• approve CI run for commit: 7015b18

Note: this should only be enabled once the PR is ready to go and can only be enabled by a maintainer