refine(tui-v3): remove redundant \n guard, visual row is sufficient

frontends/tui_v3.py

@@ -2553,6 +2553,16 @@ class SB:
         total = self.buf.count('\n') + 1
         return line_no, total, ls, le
 
+    def _logical_visual_range(self, segs, line_no):
+        """返回第 line_no 个逻辑行在 segs 中的 (first_vi, last_vi)"""
+        lines = self.buf.split('\n')
+        iw = max(1, _term()[0] - 6)
+        first = 0
+        for i in range(line_no):
+            first += max(1, len(_wrap_cells(lines[i], iw)))
+        cnt = max(1, len(_wrap_cells(lines[line_no], iw)))
+        return first, first + cnt - 1
+
     def _cur_v(self, d: int) -> None:
         """↑/↓ roam by VISUAL row (a long single-line paste wraps to many rows
         yet stays one logical line — must still roam). At the top/bottom visual
@@ -5170,11 +5180,19 @@ class SB:
                 else:
                     self._sel = None
                     line_no, total, ls, le = self._line_region()
-                    if line_no == 0:
-                        if self.pos == ls:
-                            self._nav_hist(-1)
+                    segs = self._segs(max(1, _term()[0] - 6))
+                    vi, _ = self._seg_at(segs)
+                    first_vi, _ = self._logical_visual_range(segs, line_no)
+                    if vi == first_vi:          # 在视觉首行
+                        if line_no == 0:
+                            if self.pos == ls:
+                                self._nav_hist(-1)
+                            else:
+                                self.pos = ls
+                        elif self.pos == ls:
+                            self._cur_v(-1)     # 已在行首 → 正常上移
                         else:
-                            self.pos = ls
+                            self.pos = ls       # 跳到该行行首
                     else:
                         self._cur_v(-1)
             elif o == 0x13:                       # Ctrl+S stash/restore draft
@@ -5186,11 +5204,19 @@ class SB:
                 else:
                     self._sel = None
                     line_no, total, ls, le = self._line_region()
-                    if line_no == total - 1:
-                        if self.pos == le:
-                            self._nav_hist(1)
+                    segs = self._segs(max(1, _term()[0] - 6))
+                    vi, _ = self._seg_at(segs)
+                    first_vi, last_vi = self._logical_visual_range(segs, line_no)
+                    if vi == last_vi:           # 在视觉末行
+                        if line_no == total - 1:
+                            if self.pos == le:
+                                self._nav_hist(1)
+                            else:
+                                self.pos = le
+                        elif self.pos == le:
+                            self._cur_v(1)      # 已在行末 → 正常下移
                         else:
-                            self.pos = le
+                            self.pos = le       # 跳到该行行末
                     else:
                         self._cur_v(1)
             elif o == 0x02:                       # ← caret left