fix(text-field): reconcile documented contract

[Banegasn]

Fixes #23

Summary

• establish one typed text-field API for filled/outlined variants, labels, helper/error text, counters, slots, validation, and host methods
• connect generated label, helper, and error IDs to the native input; make required, min/max length, pattern, and custom errors participate in form validation
• standardize on exactly-once native host input/change events, update the Angular demo, and document the clean-break migration from undocumented aliases
• add browser tests and package test/typecheck wiring

Acceptance mapping

• Every documented property, attribute, slot, event, method, and variant is implemented and typed, with public removals documented.
• Label activation focuses the input; label/help/error relationships use generated IDs and ARIA IDREFs.
• Required, minlength, maxlength, pattern, and custom-error validity participate through ElementInternals.
• Native-like host input and change events fire once; removed custom aliases do not fire.
• README and Angular demo use the canonical contract; browser tests cover Chromium, Firefox, and WebKit.

Validation

• pnpm build (passes; existing Angular bundle/style budget warnings)
• pnpm typecheck
• pnpm lint
• pnpm test
• pnpm --filter @banegasn/m3-text-field test (12 tests across Chromium, Firefox, and WebKit)

[Banegasn]

Acceptance review found a P1 blocker: rendered validity/ARIA can diverge from ElementInternals. Initial or dynamically added required/pattern constraints can make the form invalid after render without updating the error supporting row, aria-invalid, or aria-errormessage; disabled controls can retain an invalid visual/ARIA state after form validity clears. Synchronize a rendered validity state after input/constraint changes (respecting form-disabled state) and add browser regressions for initial required, dynamic constraints, and disabled clearing. Implementation has been returned for this focused fix.