fix(free): keep expert fret chord (e.g. VI) for no-fret pick

Do not force I on free pick; reuse last expert KEY_ID / remembered chord after mode switch.

Co-authored-by: Cursor <cursoragent@cursor.com>

Global/Global.c

@@ -647,30 +647,55 @@ void Accomp_ApplyDefaultIChord(void)
   PressFlag = 0;
 }
 
-/* 专业模式按停止键时记住当前调性，供普通模式无指板拨片起奏使用。
+/* 专业模式：记住停键时的移调，以及最后一次指板和弦（供普通无指板拨片）。
- * 0xFF=尚未在专业停过；移调合法值 0~11。 */
+ * transpose: 0xFF=尚未在专业停过；移调合法值 0~11。
+ * chord: 0=无记录；1~21=指板键。 */
 static uint8_t s_expert_stop_transpose = 0xFFu;
+static uint8_t s_expert_last_chord = 0;
 
-static void Expert_RememberStopTranspose(void)
+static void Expert_RememberLastChord(uint8_t key)
+{
+  if (key >= 1u && key <= 21u)
+    s_expert_last_chord = key;
+}
+
+static void Expert_RememberStopContext(void)
 {
   uint8_t tab = (uint8_t)mGuiData[GUI_TAB_INDEX].Current;
   uint8_t last = (uint8_t)mGuiData[GUI_TAB_LAST_INDEX].Current;
 
   if (tab == 1 || (tab == 3 && last == 1))
+  {
     s_expert_stop_transpose = (uint8_t)mGuiData[GUI_TRANSPOSE].Current;
+    Expert_RememberLastChord(KEY_ID_1629);
+  }
 }
 
-/* 普通无指板拨片：套用上次专业停键调性（无记录则保持当前移调） */
+/* 普通无指板拨片：移调用专业停键值；和弦优先当前 KEY，否则专业最后指板，再否则一级 */
-static void FreeMode_ApplyExpertStopTranspose(void)
+static void FreeMode_ApplyExpertChordForNoFretPick(void)
+{
+  if (s_expert_stop_transpose != 0xFFu &&
+      (uint8_t)mGuiData[GUI_TRANSPOSE].Current != s_expert_stop_transpose)
   {
-  if (s_expert_stop_transpose == 0xFFu)
-    return;
-  if ((uint8_t)mGuiData[GUI_TRANSPOSE].Current == s_expert_stop_transpose)
-    return;
     mGuiData[GUI_TRANSPOSE].Current = s_expert_stop_transpose;
     UITask_Sendmsg(MSG_ID_BLE_UI_REFRESH, GUI_TRANSPOSE, 0, 0);
   }
 
+  if (KEY_ID_1629 >= 1u && KEY_ID_1629 <= 21u)
+  {
+    Expert_RememberLastChord(KEY_ID_1629);
+    PressFlag = 0;
+    return;
+  }
+  if (s_expert_last_chord >= 1u && s_expert_last_chord <= 21u)
+  {
+    KEY_ID_1629 = s_expert_last_chord;
+    PressFlag = 0;
+    return;
+  }
+  Accomp_ApplyDefaultIChord();
+}
+
 void Accomp_UpdatePlayingChord(void)
 {
   uint8_t midi_note_buff[4] = {0,};
@@ -1118,7 +1143,7 @@ static void Band_AllNotesOff(void)
  * 库 Stop 之后第一个 Start 必被吞，立即拨片无声。 */
 void Stop_AutoBand_Soft(void)
 {
-  Expert_RememberStopTranspose();
+  Expert_RememberStopContext();
   FreeMode_CancelEvenBeatStop();
   Band_CancelStartFollowup();
   Band_TickGate = 0;
@@ -1133,7 +1158,7 @@ void Stop_AutoBand_Soft(void)
 
 void Stop_AutoBand()
 {  
-  Expert_RememberStopTranspose();
+  Expert_RememberStopContext();
   FreeMode_CancelEvenBeatStop();
   /* 先清播放态，再 Stop/AllNoteOff，避免处理期间其它路径误判在播 */
   Band_CancelStartFollowup();
@@ -1453,6 +1478,11 @@ void TM1629_Handle(uint8_t key)
         }
         uint8_t group = (key - 1) / 3;          /* 1~3→0, 4~6→1, ..., 19~21→6 */
         KEY_ID_1629 = key;
+        /* 专业（及设置页来自专业）：记下指板和弦，供切普通后无指板拨片沿用 */
+        if (mGuiData[GUI_TAB_INDEX].Current == 1 ||
+            (mGuiData[GUI_TAB_INDEX].Current == 3 &&
+             mGuiData[GUI_TAB_LAST_INDEX].Current == 1))
+          Expert_RememberLastChord(key);
         MIDI        = (STRING_MIDI *)Chord_Midi_Table[group];
         ORGAN_MIDI  = OrganChord_Midi_Table[group];
         
@@ -1573,7 +1603,7 @@ void Pick_Handle()
   }
 
   /* 左手未触发和弦板（或落在拍速/停止键）时：拨片默认发当前调一级大和弦伴奏。
-   * 普通模式无指板也可起奏：调性用上次专业停键时的移调，起奏后无操作则偶拍停。 */
+   * 普通无指板也可起奏：用专业最后指板和弦（如 VI），无记录才退回一级；无操作则偶拍停。 */
   {
   uint8_t free_pick_no_fret =
       (mGuiData[GUI_TAB_INDEX].Current == 2 &&
@@ -1581,8 +1611,7 @@ void Pick_Handle()
 
   if (free_pick_no_fret)
   {
-    FreeMode_ApplyExpertStopTranspose();
+    FreeMode_ApplyExpertChordForNoFretPick();
-    Accomp_ApplyDefaultIChord();
     chord_id = KEY_ID_1629;
   }
   else if (mGuiData[GUI_TAB_INDEX].Current != 2 &&