feat(core, ts-plugin, codegen)!: require cmkOptions.enabled: true to activate

[mizdra]

Summary

• Change CMKConfig.enabled type from boolean | undefined to boolean; when omitted, the value is normalized to false
• Enable ts-plugin language features and codegen only when cmkOptions.enabled is explicitly set to true in tsconfig.json (previously they worked even without the option)
• Remove the transitional warning added in Warn when cmkOptions.enabled is not set, and exit with error when cmkOptions.enabled is false #290 that advised users to set cmkOptions.enabled

Closes #289

Test plan

• vp test --project unit — all unit tests pass
• vp test --project e2e — all E2E tests pass (added enabled: true to all ts-plugin e2e fixtures)
• vp check — lint / format / type checks pass

🤖 Generated with Claude Code

[changeset-bot]

🦋 Changeset detected

Latest commit: 8f86398

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

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