fix: /simplify 리뷰 — UX/코드 품질 10건 수정

- EditableSegment: readOnly prop 추가, hover 배경색 효과
- MeetingDetailTabs: useMemo(parseSegments), 이중 debounce 제거, cleanup
- MeetingChatPanel: sessionId deps, 에러 표시, key=timestamp
- ExportMenu: i18n 위반 수정 (하드코딩 → t())
- MeetingModePage: 에러 Snackbar 피드백 (startRecording, viewDetail)
- TranscriptTab: polish 실패 피드백
- 12개 locale i18n 키 5개 추가

src/renderer/components/meeting/EditableSegment.tsx

@@ -12,6 +12,7 @@ interface EditableSegmentProps {
   text: string
   edited: boolean     // 수정 여부
   onEdit: (segmentId: string, newText: string) => void
+  readOnly?: boolean
 }
 
 function formatTimestamp(ms: number): string {
@@ -27,6 +28,7 @@ export function EditableSegment({
   text,
   edited,
   onEdit,
+  readOnly = false,
 }: EditableSegmentProps): React.ReactElement {
   const { t } = useI18n()
   const [editing, setEditing] = useState(false)
@@ -34,9 +36,10 @@ export function EditableSegment({
   const inputRef = useRef<HTMLInputElement>(null)
 
   const handleClick = useCallback(() => {
+    if (readOnly) return
     setDraft(text)
     setEditing(true)
-  }, [text])
+  }, [readOnly, text])
 
   const handleCommit = useCallback(() => {
     const trimmed = draft.trim()
@@ -104,12 +107,17 @@ export function EditableSegment({
         fontFamily: d3roFontMono,
         fontSize: 13,
         color: d3roPalette.text.primary,
-        cursor: 'text',
+        cursor: readOnly ? 'default' : 'text',
         borderBottom: edited ? `1px dashed ${d3roPalette.text.inactive}` : 'none',
-        '&:hover': {
-          color: d3roPalette.text.primary,
-          borderBottomColor: edited ? d3roPalette.accent.amber : undefined,
-        },
+        borderRadius: '2px',
+        px: readOnly ? 0 : '2px',
+        '&:hover': readOnly
+          ? {}
+          : {
+              color: d3roPalette.text.primary,
+              borderBottomColor: edited ? d3roPalette.accent.amber : undefined,
+              bgcolor: edited ? undefined : d3roPalette.bg.elevated,
+            },
       }}
     >
       {text}