test(e2e): full Playwright coverage for v0.2 + RHF discard fix

[mayrang]

Summary

Adds Playwright coverage for every public surface (both pre-existing v0.1 features that had only unit-test coverage and the new v0.2 additions), and ships one real bug fix uncovered during the e2e pass.

Test deltas:

• Unit: 201 → 202 (RHF discard regression test)
• E2E: 21 → 84 (28 scenarios × Chromium / Firefox / WebKit)
• Bundle: 5.42 KB / 8 KB unchanged

Example app

Restructured to a tiny hash router. The existing SignupWizard stays at / (so the original 7 headline scenarios are untouched), each new feature gets its own page under #/<route>. Lazy-loaded so each route only ships what it needs.

New demo pages:

Route	Demonstrates
#/conflict	multiTab: 'warn' + both <ConflictDialog> and <ConflictResolver>
#/auto-storage	autoAdapter with a 5,000-char threshold for fast migration
#/external-control	getFormDraft from a sibling + useFormDraftStatus sibling reader
#/heartbeat	createHeartbeatDetector against an intercepted /__heartbeat__ route
#/rhf #/formik #/tanstack	Each adapter wired against zod + localStorage
#/session-storage #/indexeddb	Non-default storage backends

E2E specs (7 new files)

• conflict.spec.ts (4 tests): tab-A-saves-B-sees-conflict-dialog-merges-to-correct-result, Esc keeps local, headless resolver pick-all-remote, aria-modal=true + focus contract
• auto-storage.spec.ts (2 tests): small → localStorage, bloat → IndexedDB migration with onMigration callback; discard clears both
• external-control.spec.ts (4 tests): useFormDraftStatus reactivity, external getValues / save / discard
• heartbeat.spec.ts (1 test): online → offline → online transitions
• adapters.spec.ts (6 tests): persist+restore+discard per RHF / Formik / TanStack
• storage-adapters.spec.ts (4 tests): sessionStorage + IndexedDB persist + don't-leak-to-localStorage

Bug found and fixed: RHF discard

The RHF adapter exposed discard: draft.discard raw, while Formik and TanStack adapters wrapped it to also reset the underlying form. Result:

1. discard() clears localStorage and resets draft.values to defaults
2. The RHF input still shows the stale text (RHF doesn't subscribe to draft.values after mount)
3. Worse: when I patched the adapter to also call form.reset(defaults), RHF's watch subscription fired on the reset, called draft.patch(emptyDefaults), and re-persisted the empty form back into the just-cleared draft, silently undoing the discard

Fix: added an ignoreNextWatchRef flag (same pattern as Formik's ignoreNextFormChangeRef). The watch subscriber consumes-and-clears it, skipping the patch when the reset is library-initiated (both restore and discard paths). New unit test locks the regression in.

Notable test infrastructure

• Heartbeat e2e uses page.route('**/__heartbeat__', ...) toggling instead of context.setOffline(true). Playwright's setOffline doesn't reliably intercept same-origin loopback connections to the dev server, so the route handler is the deterministic way to flip reachability.
• Conflict focus assertion brings tab B to the front + re-focuses the first dialog button before asserting document.activeElement is inside the dialog. In multi-page contexts, only one tab has window focus and programmatic .focus() on a non-active tab silently no-ops in headed Chromium.

README v0.2.0

• Banner now reflects v0.2.0 (was v0.1.0-rc.2)
• Status block: 202 unit + 84 e2e, 5.42 KB / 8 KB
• FAQ entry for "TanStack / Formik" now points at the dedicated adapters
• Contributing list drops Formik / TanStack / heartbeat (all shipped)

Test plan

• npm run typecheck — clean
• npm run lint — clean
• npm test — 202 passing
• npx playwright test — 84 passing across Chromium / Firefox / WebKit
• npm run build clean, npm run size 5.42 KB / 8 KB