Add @b9g/crank/web-components (CrankHTMLElement)

[brainkim]

Implements the class-based CrankHTMLElement from the RFC in #360 (closes #47).

What's implemented

• Static config: observedAttributes, events, formAssociated, shadowDOM, styles.
• render method (this = element, ctx = arg), all four component forms via a stable bridge.
• requestUpdate() — microtask-batched, coalescing, safe before first connect.
• Light DOM (default, render owns the subtree) or shadow DOM with native <slot>.
• Faithful on<type> handlers (lazy activate/deactivate; reassignment preserves listener order), typed from CrankHTMLElement<{events: typeof Class.events}> (names-only for a tuple, typed payloads for an event map).
• static styles derived once per class (string / CSSStyleSheet / mixed array), adopted into the shadow root or document.
• Form association: base re-renders on the four form callbacks; ElementInternals stays the author's.
• Pre-upgrade properties re-applied through their accessors on connect.
• Render errors → cancelable error event, then reportError if unhandled.
• DOM renderer widened to accept a ShadowRoot (or document fragment) as a render root.

Examples — examples/web-components.tsx

The RFC's Scope examples: x-blink (generator + timer, light DOM), x-marquee (shadow DOM, scoped static styles, imperative start()/stop(), typed static events), and x-rating (form-associated, ElementInternals value/validity, super-able reset/restore), plus a small demo wiring them together.

Tests — test/web-components.tsx, 33 passing in Chromium

Behavior: sync/async/generator/async-generator render; attribute re-render + same-value bail; requestUpdate + coalescing; generator-state persistence; shadow + slot projection; open ShadowRootInit and closed mode; on<type> firing + listener ordering; in-component error fallback; render-error event (sync + async) + reportError; form FormData/reset/:disabled; light + shadow style adoption (deduped, mixed arrays); pre-upgrade property upgrade; light-DOM child replacement; move-vs-removal teardown.
Integration: rendering a custom element through Crank's own DOM renderer; nested custom elements; ctx.refresh/schedule/after; provisions within an element; computed shadow styles; accessor→attribute reflection. Plus a compile-only check of the event typing (tuple and event-map forms).
Full suite green (606 passing); tsc --noEmit clean; build emits the ./web-components export (.js/.cjs/.d.ts).

Bugs the tests caught and this PR fixes: light DOM wasn't replacing authored children; a pre-connect requestUpdate fired a spurious extra render; pre-upgrade properties weren't upgraded.

Out of scope (deferred by the RFC)

SSR / declarative shadow DOM / hydration (RFC Appendix), the form-value SSR shim, customized built-ins, and a scoped css prop.

🤖 Generated with Claude Code

[brainkim]

thoughts on shortening this to @b9g/crank/wc?

[brainkim]

Every other crank subpath is a spelled-out word (/standalone, /dom, /html, /jsx-runtime), so /web-components matches the family; /wc would be the lone abbreviation and less greppable. I lean /web-components, but the shorter import is a trivial change if you prefer it.