refactor(core, ts-plugin, codegen): move token name validation from check phase to parse phase

[mizdra]

ref: #377

Token name validation (rejecting __proto__, default when namedExports: true is set, and names containing backslashes) was implemented in the check phase, alongside checks that require resolving other files, such as verifying that an imported token actually exists.

However, this validation only inspects names extracted from a single file and does not depend on any other file, so it is not a semantic check. This PR reclassifies it as a syntactic one: parseCSSModule now validates token names and reports violations as parse diagnostics. The messages and positions of the reported diagnostics are unchanged.

As a supplementary note, this is also groundwork for supporting TypeScript 7's content mappers (microsoft/typescript-go#4712): a content mapper reports diagnostics when parsing a file, so validations that need no cross-file information must run in the parse phase.

How to verify

• Run vp test.
• Open examples/1-basic in an editor and add .__proto__ { color: red; } to src/a.module.css. The `__proto__` is not allowed as names. error is still reported.

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[changeset-bot]

🦋 Changeset detected

Latest commit: a71b0fb

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 6 packages

Name	Type
@css-modules-kit/core	Patch
@css-modules-kit/ts-plugin	Patch
@css-modules-kit/codegen	Patch
@css-modules-kit/eslint-plugin	Patch
@css-modules-kit/stylelint-plugin	Patch
css-modules-kit-vscode	Patch

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