fix(gui): address review — stale smoke case, tooltip trigger overlap, collapse contract docs

- The real-browser collapse smoke tracked the old chrome: visible HARNESS
  text (the wordmark svg is aria-hidden now), an 'Expand sidebar' label
  (renamed 'Open sidebar'), a 300px settle (default is 280), and an
  immediate focus assert (rail search defers focus past the slide). The
  case now tracks the brand span, polls the deferred focus, and uses the
  current labels and width.
- Tooltip treated hover and focus as one trigger: leaving with the mouse
  dropped the bubble of a still-focused anchor (and vice versa). The two
  triggers are tracked independently; the bubble hides only after both
  clear. Spec pins both orders.
- The ui-sidebar README and the bilingual collapse note still described
  the retired geometry morph; both now state the slide + crossfade
  contract, the fixed-width (never-conceding) sidebar, and the rail's
  whale-mark/tooltip chrome.

packages/client/ui-sidebar/README.md

@@ -1,6 +1,6 @@
 # @deepseek-ai/dsh-client-ui-sidebar
 
-Sidebar plugin: session multi-level tree (cwd grouping + parentId nesting), search, by-workspace grouping, state dots, three creation entries. Collapse morphs the four control rows into the layout-owned 56px rail (expand / new session / new workspace / search — search expands and focuses the search box) plus the settings foot: geometry animates on the deepsuite curve while wide-only content cross-fades and unmounts at settle. Contract: the [slot system standard](../../../.agents/notes/implemented/architecture/2026-07-22-slot-type-chain-implementation.md).
+Sidebar plugin: session multi-level tree (cwd grouping + parentId nesting), search, by-workspace grouping, state dots, three creation entries. Collapse is a slide + crossfade into the layout-owned 56px rail (open / new session / new workspace / search — search expands and focuses the search box — plus the settings foot): the expanded content freezes at its width and fades in place while the column slides over it, then the rail — whale mark resting, panel icon on hover, tooltips on every control — crossfades in at settle as the wide content unmounts. Contract: the [slot system standard](../../../.agents/notes/implemented/architecture/2026-07-22-slot-type-chain-implementation.md).
 
 `src/client/contract/slots.ts` is the single-domain contract file: `SidebarRootInjected` (the registrant's own injected share — plain service callbacks: onOpen/onCreate/onToggleSidebar) and `SidebarRootComponentProps = PropsRuntime<'sidebar'> & SidebarRootInjected` (owner `{collapsed,width}` plus the standard `useSessions` hook, resolved off ui-layout's SlotMap declaration, never re-stated). `apply` registers SidebarRoot cast-free against that composition; the inject factory closes over the plugin's own ctx.