feat(design-tokens): remove default corner-radius token's reference

[matgalla]

Related Issue: #14765

Summary

• stops token build from retaining corner-radius.default's value as a reference
• remaps corner-radius.default's value to a core token

- --calcite-corner-radius: var(--calcite-corner-radius-none);
+ --calcite-corner-radius: 0;

[Copilot]

Pull request overview

Updates the design-tokens build so corner-radius.default no longer emits as a CSS custom-property reference and instead resolves to a primitive 0, aligning the generated outputs with the intended token value behavior.

Changes:

• Remapped semantic/corner-radius.default to reference the core size token {core.size.default.none}.
• Simplified stylesheetOutputReferences so corner-radius.default is no longer forced to output as a reference.
• Updated token build snapshots to expect --calcite-corner-radius: 0; (and SCSS equivalent) rather than a var() reference.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
packages/design-tokens/src/tokens/semantic/corner-radius.json	Remaps corner-radius.default to {core.size.default.none} to avoid retaining a semantic reference.
packages/design-tokens/src/config/index.ts	Removes the special-case that forced corner-radius.default to emit as a reference in stylesheets.
packages/design-tokens/tests/spec/snapshots/index.spec.ts.snap	Updates expected generated CSS/SCSS output to reflect the new primitive 0 value.