The user message bubble had hover on a `Pressable` wrapping the bubble,
with the timestamp and copy button as siblings outside it — moving the
cursor onto them lost hover. Wrapping both in a single Pressable then
flickered, because `TurnCopyButton` is itself a Pressable and nested
Pressables fight over hover state.
Rewrite `UserMessage` to match the workspace row pattern: hover-tracking
on a plain outer `View` with `onPointerEnter`/`onPointerLeave`, nested
Pressables freely inside. Pointer events are non-bubbling DOM events,
so descendants can't disrupt the outer hover.
Rewrite `docs/hover.md` with the workspace row as THE canonical pattern,
not one option among several. Names the three failure modes that come
from skipping it — including "nested Pressables fight over hover" — and
explicitly bounds when `Pressable.onHoverIn`/`onHoverOut` is acceptable
(self-styling only).
Update `constants/platform.ts` so its hover guidance points at the doc
instead of recommending the broken pattern.
Add `packages/app/src/constants/platform.ts` with canonical gates
(isWeb, isNative, getIsElectron) and refactor all ~100 ad-hoc
Platform.OS checks across 69 files to use shared imports.
Fix sidebar hover crash on native (onPointerEnter → onHoverIn),
fix tooltip to use breakpoint instead of platform detection, make
sidebar action buttons always visible on native where hover doesn't
work, and document the platform gating decision matrix in CLAUDE.md.
Mohamed Boudra