…s format (#3203)

* feat: --output-references CLI arg for build-tokens, registers filters, and updates CSS vars format

* Exposes `--output-references` CLI argument for `build-tokens` command. Defaults to `true`. Ensures brand package output with the CLI includes references in build output out-of-the-box.

* Registers filter(s) `isThemeVariant.{'light'}`, handling future theme variants when implemented (e.g., `isThemeVariant.dark`).
* Migrates `createCustomCSSVariables` to use `formattedVariables` to rely on out-of-the-box CSS variable formatting. The formatter still supports token-specific overrides of `outputReferences`. If a token has modifications via `modify`, the modified base reference is not included in the output.
* Updates custom fileHeader implementation, including a relative path to design tokens documentation.
* Fixes bug with line-height tokens, switching their `$type` from `dimension` to `number` to resolve typography style regressions.
* Updates typography tokens related to font size, font weight, and line-height for more consistent naming structure when taking into account mobile.
* Updates `@mobile-type` SCSS mixin to support level-specific customization of mobile typography styles for display 1-4.
* Renames `"description"` field in tokens to `"$description""` per the DTCG format.

* Ensures the "Typography" foundations page properly previews the correct font size for regular "Body" text and includes the missing "HEADING LABEL" example.
* Updates to "Colors" page in docs site:
  * Displays token name instead of CSS variable in the color swatch previews (see screenshot below).
  * Include `accent-a` and `accent-b` alongside other color names, rather than manually rendering `Swatch` for the accents.
  * Modifies the grid styles for color swatch preview to be more responsive.
* Resolves `NaNpx` bug in `MeasuredItem` component on docs site, while computing the measurements to display for an element (e.g., font size). Instead, it renders an empty block while measurements are resolved.
* Updates `CodeBlock` styles on docs site to add its border and background color only to the `LivePreview`, not the entire `CodeBlock` example.
* Reduces whitespace on docs site homepage.
* Simplifies columns on docs site header, ensuring `SiteTitle` is horizontally aligned in the center.

…with a period

…efs warnings

refactor: corrected expanded tokens

refactor: code refactoring

refactor: created an abstracted CSS variables

refactor: added missing expanded tokens

refactor: added missing expanded tokens

refactor: small refactoring after review

refactor: corrected imports for CSS files

feat: expanded --pgn-transition-carousel-base token, some refactoring

fix: corrected --pgn-transition-base-timing-function value

refactor: some refactoring and updates

refactor: corrected progress-bar and typography tokens

…onent