feat(): update panel scroll for events

[StuBehan]

Summary

Panel layout + scrolling fixes for the Events and Usage tabs: stop the
events list shifting left when the scrollbar appears, keep the selected
event in view, prevent the footer hint strip from reflowing, and give
the panel enough default/min width to actually fit the permission-event
footer. Also adds Up/Down keyboard scrolling on the Usage tab.

Changes

• panel/Components.swift — ThinScrollers now forces
  scrollView.scrollerStyle = .overlay, so the scrollbar floats over
  content instead of claiming layout width and shifting rows left (which
  is what users with "Show scroll bars: Always" in System Settings would
  otherwise see).
• panel/Panel.swift (Events tab)
  • Wrap the events list in ScrollViewReader, tag each row with
    .id(event.id), and on selectedID change proxy.scrollTo(..., anchor: .center)
    with a 0.15s easeOut — arrow-key navigation now keeps the selection
    in view instead of letting it leave the viewport.
  • .frame(maxHeight: .infinity) on the ScrollView so it bounds itself
    to the panel's available area (mirrors the prior Usage fix); split
    vertical padding into 4pt top / 8pt bottom so the last row clears
    the footer.
  • EventRow title now has .lineLimit(1) + .truncationMode(.tail)
    so a long title can no longer wrap and inflate row height,
    distorting rows below it.
  • Footer always renders the Snooze hint (opacity 0.35 when the
    selected row isn't snoozable) so the strip never reflows as
    selection moves between event types. S is still wired to fire
    only on snoozable rows, so the dim state matches behavior.
• panel/Panel.swift (panel sizing)
  • Default size 420×280 → 600×320 (panelDefaultSize).
  • Minimum 340×240 → 560×260 (contentMinSize + new
    panelMinWidth / panelMinHeight constants used by
    loadSavedPanelSize). Returning users with a smaller saved size
    get clamped up on next launch, so the permission-event footer
    always fits.
• panel/Panel.swift (Usage tab)
  • Up/Down arrows now scroll the Usage ScrollView. SwiftUI doesn't
    expose a programmatic delta-scroll API, so scrollUsageBy walks
    the AppKit hierarchy via findScrollView(in:) and nudges the
    NSScrollView's clip view by 40pt, clamped to
    [0, docHeight - clipHeight].

Testing

• swift build — clean.
• make reload, then sent 6 mixed test events at the panel socket (3
  permission, 3 stop, including one with a long title and one with a
  long message). Verified:
  • Scrollbar appearance no longer shifts rows left.
  • Long title row truncates with …; rows below stay aligned.
  • Arrow-down past the visible area scrolls the selection into view;
    last row clears the footer fully.
  • Footer strip width is stable as selection moves between permission
    and stop rows; Snooze dims/un-dims rather than appearing/vanishing.
  • Cmd+1-4 and Cmd+← / Cmd+→ still cycle tabs.
  • On the Usage tab, Up/Down arrows scroll the quota tier list; Esc
    still hides; other keys remain swallowed.

Related issues

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