fix: escape class values supplied to the constructor

[SAY-5]

Fixes #182.

parser.className({ value: "hover:bg-blue" }) currently serializes as .hover:bg-blue, while assigning the same value after construction correctly escapes the colon. Initialize constructor values through the existing escaping setter unless an explicit raws.value was supplied.

Keep parsed selectors lossless by retaining their original spelling and raw AST shape. Regression coverage includes identifier punctuation, leading digits, backslashes, Unicode, explicit raw spelling in either option order, cloning, and Less interpolation.

Validation on Node 26.7.0: six regression assertions fail before the fix; all 109 focused tests and all 806 full-suite tests pass afterward. Coverage gates pass (95.02% lines, 95.50% branches, 97.70% functions). Build, lint, changed-file formatting, and strict declaration checks using project-local type roots pass.

The default declaration check picks up unrelated ancestor @types/node declarations and reports three unchanged errors; the strict check with --typeRoots ./node_modules/@types passes without skipping library checks. Full formatting reports only the unchanged src/__tests__/exceptions.mjs; lint reports two existing warnings there.

OpenAI Codex assisted with the code, tests, and description. The final patch received an independent AI review.