fix(qwik): defer context access until visible lifecycle - #389

Summary

• replace render-time Qwik context dereferences with a stable NoSerialize context signal populated by the visible lifecycle
• resolve context readiness at action/task time across stream, chat, history, source, and agent hooks
• add QRL factories for SSR-resumable hook-owned contexts and custom sources while preserving client-only direct-object support
• add optimizer-backed rendered lifecycle regressions and document the lifecycle contract

Closes #372.

Why

Qwik component setup runs before useVisibleTask$. The adapter previously destructured a getter backed by a local context variable during setup, permanently capturing the unavailable value. Optimizer-backed rendering also demonstrated that mutating that captured local is incompatible with Qwik's transformed lifecycle.

The new ctxRef signal keeps the render-time reference stable while the browser-only context remains NoSerialize. Dependent hooks read it only when a visible task or action actually needs the context.

Validation

• npm run build -w @askable-ui/qwik
• npm test -w @askable-ui/qwik — 29 tests, including 5 optimizer-backed rendered lifecycle tests
• npm audit --omit=dev --audit-level=high
• npm run build
• npm test — 1,162 tests
• npm ci && npm run build in site/docs
• git diff --check

Follow-up

Optimizer-backed investigation also found the broader pre-existing Qwik action-QRL limitation tracked separately in #388. This PR stays focused on context readiness and does not introduce a breaking action/callback API migration.