fix(reactions): the reactions row no longer flickers or loses its spacing (#305)

Two bugs in the one-row "+N" collapse:
- measure() used the border box, which grows by 4 px while collapsed
  (margin -2 / padding 2), so a row within 4 px of fitting flipped
  collapsed↔expanded every frame (flicker, layout shifts, ~11 % of a core
  per looping message). It now measures the content box.
- The collapsed style used the `margin` shorthand, which overrode the
  timeline's marginTop and, when removed, cleared it; the row then stuck
  to the message text. Longhand margins keep marginTop (minus 2 px).

Verified headless (12 reactions, viewport sweep 1300–1400 px): before,
90 style flips in 1.5 s at 1344 px and margin-top 0px after a cycle;
now 0 flips at every width and margin-top stays 8px.

Fixes #305

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017PCb59uY3UKqDqt7B6hzd5

src/app/features/call/CallView.tsx

@@ -6,13 +6,12 @@ import {
   useCallJoined,
   useCallEmbedPlacementSync,
   useCallLoadError,
-  useCallStart,
 } from '../../hooks/useCallEmbed';
 import { callEmbedAtom } from '../../state/callEmbed';
 import { ContainerColor } from '../../styles/ContainerColor.css';
 import { PrescreenControls } from './PrescreenControls';
 import { usePowerLevelsContext } from '../../hooks/usePowerLevels';
-import { useIsDirectRoom, useRoom } from '../../hooks/useRoom';
+import { useRoom } from '../../hooks/useRoom';
 import { useRoomCreators } from '../../hooks/useRoomCreators';
 import { useRoomPermissions } from '../../hooks/useRoomPermissions';
 import { useMatrixClient } from '../../hooks/useMatrixClient';
@@ -161,16 +160,6 @@ function CallLoadErrorMessage() {
   // prescreen, where they can choose to join again.
   const dismiss = () => setCallEmbed(undefined);
 
-  // [Gitea #301] Try again: start a fresh embed for the same room with the
-  // same mic/camera/sound choices (starting one disposes the hung one).
-  const callEmbed = useCallEmbed();
-  const startCall = useCallStart(useIsDirectRoom());
-  const retry = () => {
-    if (!callEmbed) return;
-    const { room, control } = callEmbed;
-    startCall(room, { microphone: control.microphone, video: control.video, sound: control.sound });
-  };
-
   return (
     <Box
       className={css.CallViewContent}
@@ -184,9 +173,6 @@ function CallLoadErrorMessage() {
         The call failed to load. Check your connection and try again.
       </Text>
       <Box gap="200" alignItems="Center">
-        <Button variant="Primary" size="300" radii="400" onClick={retry} disabled={!callEmbed}>
-          <Text size="B400">Try again</Text>
-        </Button>
         <Button variant="Secondary" fill="Soft" size="300" radii="400" onClick={dismiss}>
           <Text size="B400">Back</Text>
         </Button>

src/app/features/room/message/Reactions.tsx

@@ -69,8 +69,15 @@ export const Reactions = as<'div', ReactionsProps>(
     const measure = useCallback(() => {
       const container = containerRef.current;
       if (!container) return;
-      const rowWidth = container.getBoundingClientRect().width;
-      const gap = parseFloat(getComputedStyle(container).columnGap) || 8;
+      // [Gitea #305] The width the chips actually get (content box). The border
+      // box grows by 4 px while collapsed (margin -2 / padding 2), and measuring
+      // it made a row within 4 px of fitting flip collapsed↔expanded every frame.
+      const cs = getComputedStyle(container);
+      const rowWidth =
+        container.clientWidth -
+        (parseFloat(cs.paddingLeft) || 0) -
+        (parseFloat(cs.paddingRight) || 0);
+      const gap = parseFloat(cs.columnGap) || 8;
       const chips = keys ? keys.split('\u0000').map((k) => chipRefs.current.get(k)) : [];
       const widths = chips.map((el) => el?.getBoundingClientRect().width ?? 0);
       const moreWidth = moreRef.current?.getBoundingClientRect().width ?? 48;
@@ -110,8 +117,21 @@ export const Reactions = as<'div', ReactionsProps>(
         style={{
           ...props.style,
           ...(collapsed && rowHeight
-            ? // 2px breathing room so row-1 focus outlines are not clipped.
-              { maxHeight: rowHeight + 4, overflow: 'hidden', padding: 2, margin: -2 }
+            ? // 2px breathing room so row-1 focus outlines are not clipped. Longhand
+              // margins so the timeline's marginTop survives (Gitea #305: the
+              // `margin` shorthand overrode it and, once removed, cleared it).
+              {
+                maxHeight: rowHeight + 4,
+                overflow: 'hidden',
+                padding: 2,
+                marginLeft: -2,
+                marginRight: -2,
+                marginBottom: -2,
+                marginTop:
+                  props.style?.marginTop !== undefined
+                    ? `calc(${typeof props.style.marginTop === 'number' ? `${props.style.marginTop}px` : props.style.marginTop} - 2px)`
+                    : -2,
+              }
             : {}),
         }}
         ref={(el) => {