chore: reduce rollup import usage

[zettca]

• reduce rollup-specific imports (just types, no impact)
• migrate CJS __dirname to import.meta.dirname

[Copilot]

Pull request overview

This PR reduces direct rollup type imports within the App Shell Vite plugin code and modernizes the shared Vite config to use import.meta.dirname instead of a CJS-style __dirname shim, aiming to keep behavior unchanged while decreasing Rollup-coupled typing.

Changes:

• Removed rollup-specific type imports (NormalizedOutputOptions, OutputBundle) and relied on Vite-provided typing/context.
• Updated the cross-origin HTML transform helper to type bundle via IndexHtmlTransformContext["bundle"] and made bundle access null-safe.
• Refactored the shared .config/vite.config.ts to use import.meta.dirname and simplified path.resolve(...) calls, while inlining Rollup output options.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
packages/app-shell-vite-plugin/src/vite-importmap-plugin.ts	Drops direct Rollup output-options type import while keeping the same generateBundle behavior.
packages/app-shell-vite-plugin/src/vite-crossorigin-fix-plugin.ts	Replaces Rollup bundle type with Vite’s IndexHtmlTransformContext bundle typing and adds optional bundle access.
packages/app-shell-vite-plugin/src/vite-configuration-processor-plugin.ts	Removes Rollup and Vite config type annotations from hook signatures without changing logic.
.config/vite.config.ts	Migrates from computed __dirname to import.meta.dirname and consolidates Rollup output config inline.