bug(resolver): resolve hyphenated aliases and preserve var() fallback syntax

[Hebilicious]

Problem

resolveValue() in lib.ts at 94bf4d8 uses:

/var\(--(\w+)\)/g

This only recognizes a narrow var(--word) form. A declared alias containing a hyphen is silently left unresolved. Even a simple alias stops resolving when used with a fallback or permitted whitespace.

Reproduction

Given:

const map = new Map([
  ["--surface-muted", "--palette-gray-100"],
  ["--bg", "--palette-gray-100"],
]);

The current replacement expression produces:

Input	Actual	Expected reference
var(--bg)	var(--palette-gray-100)	Already correct
var(--surface-muted)	var(--surface-muted)	var(--palette-gray-100)
var(--bg, red)	var(--bg, red)	var(--palette-gray-100, red)
var( --bg )	var( --bg )	The alias is replaced; harmless whitespace may be preserved

These outputs were reproduced by executing the exact replacement expression in isolation. This is not a claim that the full repository suite was run.

A consumer-facing case is a primitive with variables: { "surface-muted": "palette.gray.100" } and a value of var(--surface-muted).

Proposed fix

Resolve the custom-property name inside actual CSS var() functions without treating fallback text or quoted text as a flat regular-expression match. A small value parser/tokenizer is preferable to extending \w and accidentally mishandling nested fallbacks.

Preserve CSS references: substitute alias names, not token values. Unmapped/external custom properties must continue to pass through unchanged.

Acceptance criteria

• Declared hyphenated aliases resolve correctly.
• Aliases with fallbacks, nested fallbacks, and permitted whitespace resolve without losing fallback content.
• Multiple references inside values such as gradients and calc() work.
• Text resembling var(...) inside quoted strings is not rewritten as a function.
• Unmapped external variables remain unchanged, preserving the existing native-CSS escape hatch.
• Unit tests cover the table above and an end-to-end primitive/gradient example.
• The supported alias-name contract is documented and aligned with token-name validation.