fix(mobile): deep-audit structural fixes — dialogs, toasts, call bar (N1)

From the 6-agent deep per-feature audit. Mobile-gated / consistency fixes;
desktop unchanged except two intentional dialog-width normalizations noted below.

- In-call control bar: wrap="Wrap" on the SequenceCard so the compact two-group
  row wraps on the narrowest phones (<=390px) instead of pushing End off-screen
  (M1 fixed the 500-750px band; this covers narrower). Desktop stays one row.
- In-call soundboard popout: clamp maxWidth to the viewport (like M5's screenshare
  popover) so it can't overflow a narrow phone.
- Report-Message dialog + "Seen by" (EventReaders) modals (Message.tsx x2 +
  RoomViewFollowing): add useModalStyle so they go full-screen on mobile like
  their sibling report/receipt modals (they floated as fixed cards before).
- In-app toast container: full-width toasts inset from both edges on mobile
  (ScreenSize.Mobile); a fixed 280-340px card previously overflowed a narrow
  phone. Desktop byte-identical (bottom-right floating card).
- Policy-list tabs + audio-controls rows: wrap="Wrap" (inert on desktop).

Intentional desktop deltas (normalizing to existing sibling modals, verified by
two review passes as consistent, not regressions): Report dialog max-width
380->480px; EventReaders modals 460->360px.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/features/call/CallControls.tsx

@@ -387,6 +387,7 @@ export function CallControls({ callEmbed }: CallControlsProps) {
         radii="500"
         alignItems="Center"
         justifyContent="SpaceBetween"
+        wrap="Wrap"
       >
         <Box alignItems="Center" gap="Inherit" grow="Yes" direction={compact ? 'Column' : 'Row'}>
           <Box shrink="No" alignItems="Inherit" justifyContent="Inherit" gap="200">

src/app/features/call/CallSoundboard.tsx

@@ -135,7 +135,12 @@ export function CallSoundboard({ callEmbed }: CallSoundboardProps) {
             escapeDeactivates: stopPropagation,
           }}
         >
-          <Menu style={{ maxWidth: manage ? toRem(420) : toRem(340), maxHeight: '70vh' }}>
+          <Menu
+            style={{
+              maxWidth: `min(${manage ? toRem(420) : toRem(340)}, calc(100vw - 2 * ${config.space.S400}))`,
+              maxHeight: '70vh',
+            }}
+          >
             <Box direction="Column" style={{ maxHeight: '70vh' }}>
               <Box
                 shrink="No"