fix(web): give History/Network/Logging list scrollbars a gutter, hide when idle (#1474) (#1475)

* fix(web): give History/Network/Logging list scrollbars a gutter, hide when idle (#1474)

The three main-content list panels rendered their ScrollArea.Autosize with
the default type="hover" and no offsetScrollbars, so the scrollbar popped in
on hover and overlaid the right edge of the cards (occluding the action
icons / status badges).

Add `offsetScrollbars` (reserves a 12px gutter so the bar never overlaps the
cards) and `type="scroll"` (the bar shows only during active scrolling, then
fades — no hover-pop) to HistoryListPanel, NetworkStreamPanel, and
LogStreamPanel. Verified in a real browser; adds a story assertion guarding
the gutter + idle-hidden behavior.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* test(web): assert scrollbar gutter on all three list panels (#1475 review)

Per review, regression-protect the gutter + idle-hidden scrollbar in every
panel, not just History. Extract the assertion into a shared
`expectScrollbarGutterIdleHidden` helper and use it from the History,
Network, and Logging panel stories.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* test(web): assert a scrollbar exists so idle-hidden check isn't vacuous (#1475 review)

Add `expect(scrollbars.length).toBeGreaterThan(0)` before the loop so the
idle-hidden assertion is meaningful rather than trivially-true if a future
change stops rendering the scrollbar element.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

clients/web/src/components/groups/LogStreamPanel/LogStreamPanel.tsx

@@ -110,6 +110,8 @@ export function LogStreamPanel({
         <ScrollArea.Autosize
           viewportRef={viewportRef}
           mah="calc(100vh - var(--app-shell-header-height, 0px) - 150px)"
+          type="scroll"
+          offsetScrollbars
         >
           <Stack gap="xs">
             {filteredEntries.map((entry, index) => (