Fix regression causing off-by-one pager height on truncated autosuggestion

Commit c54131c8c5 (Make at least one character of the autosuggestion
always shown, 2025-01-26) draws autosuggetion until exactly the end
of the line, possibly truncated by an ellipsis.  The line is "barely"
soft-wrapped; no characters or cursors are on the next line.

This means that the pager can start there (on the next line).
The calculation for available pager height fails to recognize that.
Fix that.

src/screen.rs

@@ -457,7 +457,20 @@ struct ScrolledCursor {
             self.desired.add_line();
         }
 
-        let full_line_count = self.desired.cursor.y + calc_prompt_lines(&layout.left_prompt);
+        let full_line_count = self.desired.cursor.y
+            - if self.desired.cursor.x == 0
+                && self
+                    .desired
+                    .cursor
+                    .y
+                    .checked_sub(1)
+                    .is_some_and(|y| self.desired.line_datas[y].is_soft_wrapped)
+            {
+                1
+            } else {
+                0
+            }
+            + calc_prompt_lines(&layout.left_prompt);
         let pager_available_height = std::cmp::max(
             1,
             curr_termsize

tests/checks/tmux-pager.fish

@@ -0,0 +1,24 @@
+#RUN: %fish %s
+#REQUIRES: command -v tmux
+#REQUIRES: test -z "$CI"
+
+set -g isolated_tmux_fish_extra_args -C '
+    history append ": $(string repeat $COLUMNS A)"
+    complete : -a \'(seq (math "$LINES * $COLUMNS"))\'
+'
+
+isolated-tmux-start
+
+isolated-tmux send-keys : Space Tab Tab
+tmux-sleep
+isolated-tmux capture-pane -p
+# CHECK: prompt 0> : AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA…
+# CHECK: 1    135  269  403  537  671
+# CHECK: 2    136  270  404  538  672
+# CHECK: 3    137  271  405  539  673
+# CHECK: 4    138  272  406  540  674
+# CHECK: 5    139  273  407  541  675
+# CHECK: 6    140  274  408  542  676
+# CHECK: 7    141  275  409  543  677
+# CHECK: 8    142  276  410  544  678
+# CHECK: rows 1 to 8 of 134