fix(v2): Vite 8 compatible manifest plugin

[birkskyum]

Moving to vite 8 w/ rolldown removes an entire category of dev/prod differences with vite 7 having esbuild (dev) + rollup (prod).

Towards

• [Feature]: Vite 8 / Rolldown Compatibility #2075

This PR contains:

• Vite 8 & Rolldown Support: Updated the solid-start:manifest-plugin to correctly resolve the client manifest during SSR builds under Vite 8 / Rolldown. It automatically detects the current major Vite version, and then:
  • For Vite 7: Continues to extract the .vite/manifest.json directly from the globalThis.START_CLIENT_BUNDLE memory footprint like before.
  • For Vite 8+: Falls back to reading the fully generated .solid-start/client/.vite/manifest.json from the filesystem, solving undefined 'source' TypeErrors caused by changes to Rolldown's generateBundle asset handling.

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Latest commit: aaa5c51

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commit: aaa5c51

[huseeiin]

when still using vite 7 and this pr, size gets larger 😢

@solidjs/start@alpha: 103.4 kb
pr: 115.5 kb

[birkskyum]

when still using vite 7 and this pr, size gets larger 😢

@solidjs/start@alpha: 103.4 kb
pr: 115.5 kb

Ugh, that are some rough numbers - considering build size is a key selling point of SolidStart.

[birkskyum]

I don't know if the build size increase came from this PR, or rather from:

• feat(2.0): seroval json mode #2042

[bondehagen]

@katywings If increased build size is not coming from this PR, can this be merged now?