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/pages/MeetingModePage.tsx

@@ -6,6 +6,8 @@ import {
   Box,
   LinearProgress,
   TextField,
+  Snackbar,
+  Alert,
 } from '@mui/material'
 import AddIcon from '@mui/icons-material/Add'
 import StopIcon from '@mui/icons-material/Stop'
@@ -50,6 +52,7 @@ export function MeetingModePage(): React.ReactElement {
 
   // 상세 뷰 상태
   const [detail, setDetail] = useState<MeetingSessionDetail | null>(null)
+  const [snackbarMsg, setSnackbarMsg] = useState<string | null>(null)
 
   // ── 세션 목록 로드 ──
   const loadSessions = useCallback(async () => {
@@ -140,8 +143,10 @@ export function MeetingModePage(): React.ReactElement {
       setElapsedMs(0)
       setProgress(null)
       setView('recording')
+    } else {
+      setSnackbarMsg(t('meeting.startRecordingError'))
     }
-  }, [])
+  }, [t])
 
   const handleStopRecording = useCallback(async () => {
     await window.electronAPI.meetingMode.stopRecording()
@@ -171,8 +176,10 @@ export function MeetingModePage(): React.ReactElement {
     if (resp.success) {
       setDetail(resp.data)
       setView('detail')
+    } else {
+      setSnackbarMsg(t('meeting.viewDetailError'))
     }
-  }, [])
+  }, [t])
 
 
   // ── 유틸 ──
@@ -198,6 +205,19 @@ export function MeetingModePage(): React.ReactElement {
     }
   }
 
+  const snackbar = (
+    <Snackbar
+      open={snackbarMsg !== null}
+      autoHideDuration={4000}
+      onClose={() => setSnackbarMsg(null)}
+      anchorOrigin={{ vertical: 'bottom', horizontal: 'center' }}
+    >
+      <Alert severity="error" onClose={() => setSnackbarMsg(null)} sx={{ width: '100%' }}>
+        {snackbarMsg}
+      </Alert>
+    </Snackbar>
+  )
+
   // ── 렌더: 목록 뷰 ──
   if (view === 'list') {
     return (
@@ -263,6 +283,7 @@ export function MeetingModePage(): React.ReactElement {
             ))}
           </Box>
         )}
+        {snackbar}
       </Box>
     )
   }
@@ -328,7 +349,8 @@ export function MeetingModePage(): React.ReactElement {
                   timestamp={Math.max(0, seg.timestamp - (recordingStartRef.current || seg.timestamp))}
                   text={seg.text}
                   edited={false}
-                  onEdit={() => { /* 녹음 중 편집 비활성 */ }}
+                  onEdit={() => { /* no-op: readOnly=true */ }}
+                  readOnly
                 />
               ))}
             </Box>
@@ -403,6 +425,7 @@ export function MeetingModePage(): React.ReactElement {
             </PhosphorText>
           </Box>
         )}
+        {snackbar}
       </Box>
     )
   }