vp migrate: @vitest/* not consistently catalog-referenced in catalog-managed projects

[fengmk2]

Problem

When migrating a project that uses a pnpm default catalog: for its toolchain, vp migrate handles @vitest/* inconsistently with vitest:

• It injects a browser provider (@vitest/browser-playwright) into the catalog, but references it as a concrete version in package.json instead of catalog:, leaving that catalog entry unused.
• It aligns a pre-existing @vitest/* (@vitest/coverage-v8) to the bundled version as a concrete spec and does not move it into the catalog, even though vitest itself is catalog:.

Net effect: vitest is catalog:, but the @vitest/* packages are concrete, and one of them also carries a dead catalog entry.

Reproduction

fengmk2/npmx.dev#27, migrated with vite-plus 0.0.0-commit.fcd4a979bd79b8328dd3318e451fc135242c0e4b.

pnpm-workspace.yaml:

catalog:
  vitest: 4.1.9
  '@vitest/browser-playwright': 4.1.9   # added by migrate

root package.json:

{
  "vitest": "catalog:",
  "@vitest/browser-playwright": "4.1.9",  // concrete, should be "catalog:"
  "@vitest/coverage-v8": "4.1.9"          // concrete, not in the catalog
}

The catalog's @vitest/browser-playwright entry is referenced by no package.

Expected

docs/guide/migrate-rules.md states: "When migration injects a provider into a catalog-capable project, it uses the preferred catalog and adds the provider at the bundled Vitest version." So:

1. Bug: @vitest/browser-playwright should be catalog: in package.json (matching the catalog entry the migrate already created), not a concrete spec.
2. Consistency: for a catalog-managed toolchain, aligned lockstep @vitest/* (e.g. @vitest/coverage-v8) arguably belong in the catalog too, referenced via catalog:, rather than a concrete spec that duplicates the version the catalog already tracks for vitest.

Suggested fix

• When injecting a browser provider into a catalog-capable project, write catalog: in package.json (the catalog entry is already added).
• Consider catalog-izing aligned @vitest/* lockstep packages when the toolchain is catalog-managed, so vitest and its ecosystem share one source of truth.