dogfood: fix hover-card, dropdown submenu, sonner on iOS/touch

[vivek7405]

Problem

Dogfood QA on a real iPhone (iOS 18.7 / Safari 26.5), AFTER the #730 marker-crash fix landed, found three Tier-2 components still broken on touch. All the rest now work. Fix all three in a SINGLE PR.

1. hover-card: opens only on mouseenter / focusin. Touch has no hover, so a tap falls through to the inner <a href> and the client router navigates (looks like a page "refresh"; it is NOT prefetch). Tapping the trigger should open the card and not navigate the link.
2. dropdown-menu submenu: the sub-trigger opens the submenu on pointer-enter and closes on pointer-leave, so on touch the submenu is only open while the finger is held down. A tap should toggle the submenu open and keep it open.
3. sonner: the demo "Show toast" button calls toast.success() via a dynamic import. The import path (/components/ui/sonner.ts, HTTP 200) and the toast.success export both verified, but a Chromium + desktop-WebKit triage shows the toast does NOT render even on desktop (clicked=true, <ui-sonner> mounted, but no toast node appears). So sonner is broader than iOS, likely the <ui-sonner> viewport signal re-render or where the toast node is placed.

Design / approach

• hover-card + dropdown share a root cause: hover/pointer-only interaction with no touch path. Add a pointer-type-aware tap path (e.g. @click / pointerdown with pointerType === 'touch', or a coarse-pointer check) that opens (hover-card) / toggles (submenu) without breaking mouse hover or keyboard nav. For hover-card the tap handler must preventDefault() the inner link navigation on the first tap (open), letting a second tap follow the link, or open without consuming the link per the agreed UX.
• sonner is a separate, desktop-reproducible bug: root-cause why toast() does not produce a visible toast (the items signal re-render in <ui-sonner>, the toaster singleton routing in connectedCallback, or the toast node placement), then fix.

Implementation notes (for the implementing agent)

• Where to edit (registry is the source; scripts/copy-registry.js mirrors it into the ui-website):
  • packages/ui/packages/registry/components/hover-card.ts (UiHoverCardTrigger; open handlers _showTimer/_hideTimer, the control lookup a[href], button, ... ~L90).
  • packages/ui/packages/registry/components/dropdown-menu.ts (UiDropdownMenuSub / UiDropdownMenuSubTrigger; submenu open/close + dropdownMenuSubTriggerClass).
  • packages/ui/packages/registry/components/sonner.ts (toaster singleton ~L64, toast() export ~L?, <ui-sonner> connectedCallback sets toaster.add = this._add ~L152, items = signal<ToastItem[]>([]) ~L140, _add/addToast ~L165, render() with repeat).
  • Demos: packages/ui/packages/website/app/docs/components/[name]/examples.ts (sonner demo at L529 onclick="import('/components/ui/sonner.ts').then(m => m.toast.success(...))").
• Landmines:
  • iOS-only bugs (1, 2) do NOT reproduce on desktop WebKit or Playwright iPhone emulation (proven on dogfood: all tier-2 ui components dead on iOS (slot hydration); tap does nothing #730: a local WebKit 26.4 + iPhone-emulated WebKit both bind/behave fine). So verification needs the on-device loop; a temporary gated diagnostic page is the proven method (see dogfood: all tier-2 ui components dead on iOS (slot hydration); tap does nothing #730 PRs chore: diag v10 - instrument core binding path (#730) (TEMP) #741-chore: diag v12 - surface the iOS createInstance throw (#730) (TEMP) #743). Remove any such scaffolding before the fix PR is ready.
  • sonner (3) IS reproducible on desktop Chromium/WebKit, so fix + verify it locally first.
  • Do NOT regress mouse-hover or keyboard behaviour. Hover-card's inner <a> must still navigate with JS off (progressive enhancement).
  • <ui-sonner>'s connectedCallback overwrites the singleton toaster so the last-mounted instance wins (noted in examples.ts ~L916); multiple <ui-sonner> on one page is a known gotcha.
• Invariants: light-DOM slot components; signals are the state primitive (read via signal.get() in render()); no class-field reactive props; tag-prefixed CSS in light DOM. Build on dogfood: all tier-2 ui components dead on iOS (slot hydration); tap does nothing #730 (MARKER='wjm-').
• Tests + docs: browser tests (packages/core or a ui-package test layer) for the interaction + the sonner render (Chromium-runnable for sonner); update component docs/examples if the interaction contract changes.

Acceptance criteria

• hover-card opens on tap (touch) without navigating the inner link; mouse hover still opens it; JS-off the link still navigates.
• dropdown submenu opens and STAYS open on tap (touch); mouse hover still works; keyboard arrow/Escape nav unaffected.
• sonner toast renders when triggered (fix the desktop-reproducible failure first; then confirm on iOS).
• Tests cover each change at the layer it touches; the sonner render has a Chromium browser test; a counterfactual proves it fires.
• All three fixed in a SINGLE PR; any on-device diagnostic scaffolding removed before merge.

[vivek7405]

Reopening: the #746 hover-card touch fix is incomplete on REAL iOS (passes under Chromium iPhone emulation + the live e2e, but on a physical iPhone the card opens then does not STAY open). Hypothesis: iOS fires synthetic mouseenter/mouseleave/focusin/focusout on tap, hitting the un-guarded _onEnter/_onLeave hover handlers (sonner + dropdown confirmed working). Shipping a touch-guard on the hover handlers + an on-device event logger to confirm.