fix: harden and de-slop the merged sidebar/chat/settings batch

Post-merge follow-ups for #2740 #2735 #2734 #2690 #2676 #2738 #2684
#2689 #2733 #2739 #2462 #2687 #2736 #2618 #2697, plus three regressions
found while reviewing them:

- ctrl/cmd+digit while typing no longer switches session tabs (#2503 was
  still open in practice: the guard only covered the mod+alt surface binding)
- Shiki template-call sanitizer now covers every bundled grammar, including
  the js/ts aliases and embedding grammars; timed-out highlight requests are
  memoized and no longer cancel unrelated in-flight requests
- settings flush on suspend uses keepalive and also fires on Capacitor
  appStateChange; keeps the selected model persisted across mode switches
- remote-only branches fetch before checkout; range helpers fail clearly
- git status invalidation now fires for runtime adapters too
- settings number inputs and select triggers size in ch so they scale with
  the interface font
- recent-activity timestamps tick from one list-level ticker
- Markdown preview find goes through the shared find_in_file keybind with
  containment, no longer counts its own bar, and debounces observer runs
- #2676 reverted; #2524 fixed by fading the sticky header's own background
  instead of overlaying the content below it
- sticky group headers in the model picker and sidebar render again
  (oc-sticky-fade-scroller class restored after 9b9d7069c)
- project switcher names are left-aligned again (wrapper lost in 26dbc2f30)
- tool card quick-open icon is always visible and opens the same line as the
  expanded card's button
- tautological tests replaced or removed; new oxlint findings fixed

packages/ui/src/components/session/sidebar/projects/SessionProjectScroller.tsx

@@ -248,7 +248,7 @@ function SessionProjectScrollerComponent(props: Props): React.ReactNode {
         hideTopScrollShadow={!enableStickyFade}
         scrollShadowSize={96}
         outerClassName="flex-1 min-h-0"
-        className="oc-sidebar-scroller space-y-1.5 pb-1 pl-2.5 pr-2 [overflow-anchor:none]"
+        className="oc-sidebar-scroller oc-sticky-fade-scroller space-y-1.5 pb-1 pl-2.5 pr-2 [overflow-anchor:none]"
         onScroll={enableStickyFade ? (event) => syncTopFade(event.currentTarget) : undefined}
       >
       {model.topContent}