feat(caption): let live captions use their own speech model

The speech engine now keeps an auxiliary model next to the dictation model
and transcribes with whichever the request names, reloading it once if the
engine restarted. Settings > STT gains a live-caption model so captions can
run on large-v3-turbo while dictation keeps its own model. The runtime
minimum rises to 1.7.0 because older engines would silently ignore the
model choice.

Suggestion paging moves to Up/Down: the page follows the selection and the
last item waits while more candidates are being generated. The Left/Right
page shortcuts are removed; they did nothing until a page had filled and
clash with Intel's display-rotation hotkeys.

apps/desktop/tests/main/services/SuggestionService.test.ts

@@ -346,21 +346,25 @@ describe('SuggestionService warm-up', () => {
     expect(internal._lastSkipReason).not.toBe('rate-limited')
   })
 
-  it('pageNext는 다음 페이지 첫 항목으로, 후보가 없는 페이지면 그대로 둔다', async () => {
+  it('마지막 후보에서 아직 더 만드는 중이면 next 는 제자리, 다 만들었으면 처음으로 돌아간다', async () => {
     const { getSuggestionService } = await import('../../../src/main/services/SuggestionService')
     const service = getSuggestionService()
-    const internal = service as unknown as { _candidates: Array<{ text: string; rank: number }> }
-    internal._candidates = Array.from({ length: 5 }, (_v, i) => ({ text: `후보${i}`, rank: i }))
+    const internal = service as unknown as {
+      _candidates: Array<{ text: string; rank: number }>
+      _filling: boolean
+    }
+    internal._candidates = Array.from({ length: 4 }, (_v, i) => ({ text: `후보${i}`, rank: i }))
 
-    expect(service.getState().activeIndex).toBe(0)
-    service.pageNext()
+    for (let i = 0; i < 3; i += 1) service.next()
+    // 3번째(0-based 3)에서 ↓ — 4번째 칸이 곧 페이지 2 로 넘어간 상태다.
     expect(service.getState().activeIndex).toBe(3)
-    service.pageNext()
-    // 5개뿐이라 다음 페이지가 없다 — 그대로 둔다.
+
+    internal._filling = true
+    service.next()
     expect(service.getState().activeIndex).toBe(3)
-    service.pagePrev()
-    expect(service.getState().activeIndex).toBe(0)
-    service.pagePrev()
+
+    internal._filling = false
+    service.next()
     expect(service.getState().activeIndex).toBe(0)
   })