feat(core, ts-plugin, codegen, vscode): support scoping container names via cmkOptions.container

[mizdra]

Summary

This PR adds a new option cmkOptions.container (default: false), inspired by the container option of lightningcss's CSS Modules support.

When enabled, container names are treated as tokens:

• Names declared with container-name: foo or container: foo / inline-size are added to the generated .d.ts file.
• The name in @container foo (...) is treated as a usage of that token. Language features such as Go to Definition, Find All References, and Rename work across them, and an error is reported if the referenced name is not declared.

Following lightningcss and css-conditional-5, the keywords none / and / not / or, the CSS-wide keywords, and default are not treated as container names. See docs/design.md for why local(...) / global(...) are not interpreted.

How to verify

Open examples/1-basic (where cmkOptions.container is enabled) in an editor and try Go to Definition / Find All References / Rename on the container names in src/a.module.css:

:root {
  container-name: container;
}
@container container (width > 400px) {}

🤖 Generated with Claude Code

[changeset-bot]

🦋 Changeset detected

Latest commit: 7d32920

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	Minor
@css-modules-kit/ts-plugin	Minor
@css-modules-kit/codegen	Minor
css-modules-kit-vscode	Minor
@css-modules-kit/eslint-plugin	Minor
@css-modules-kit/stylelint-plugin	Minor

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