Skip ghost band on empty-space click to remove MouseUp jiggle

The optimistic ghost paints the band at the cursor's exact Y, but
the editor's actual scroll lands at a line-snapped offset
(floor(scrollOffset / lineHeight)), so the eventual settled band
position is up to barHeight/totalLines away from the ghost. During
drag that mismatch is invisible because the cursor is moving; on a
stationary empty-space click it shows up as a one-pixel-to-many-
pixel jiggle the moment the ghost clears on MouseUp.

Fix: in OnMouseLeftButtonDown's empty-space branch, send the scroll
request directly without setting _dragGhostBandTop. The natural
ViewportState propagation (editor scrolls -> layout -> ScrollChanged
-> Viewport update -> bar invalidate -> repaint) lands the band at
its actual settled position on the next frame, which is exactly
where MouseUp will leave it. No ghost = no jiggle.

If a drag follows the click, the first MouseMove activates the
ghost via EmitDragScroll on the existing smooth-drag path. The
brief transition from natural-position-band to ghost-at-cursor is
masked by ongoing motion.

The band-grab drag case still ends with a line-snap mismatch on
MouseUp, but it's masked by the motion of the drag itself; the
user hasn't reported it as jiggle.

AI-Local-Session: b53d5fe5-38cc-41dd-b987-3def5ef3f0d3
AI-Cloud-Session: 744dd836-01e5-48af-91db-daa8241a01d7
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: geevensingh

CHANGELOG.md

@@ -41,7 +41,12 @@ body. Keep section headings exact and write notes in Markdown.
   indicator) recenters the indicator on the cursor and starts a
   drag in the same gesture — minimap-style "click anywhere to jump
   there", and a press-and-drag from empty space scrubs without
-  needing a second click.
+  needing a second click. Empty-space clicks land the indicator at
+  its actual line-snapped position immediately rather than locking
+  to the cursor on press and snapping on release — no more jiggle
+  when the press and release land at the same cursor position but
+  the editor's per-line scroll granularity doesn't divide the bar's
+  pixel height evenly.
 - Language-aware syntax highlighting for TypeScript (`.ts`, `.tsx`),
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DiffViewer/Rendering/HunkOverviewBar.cs

@@ -363,15 +363,26 @@ protected override void OnMouseLeftButtonDown(MouseButtonEventArgs e)
         bool inBand = band is not null && HunkOverviewBarGeometry.IsInsideBand(band, p);
 
         // Empty press: minimap-style "click anywhere to jump there".
-        // The band's center snaps to the cursor immediately, then any
-        // continued motion drags from there — empty-space press and
-        // empty-space-press-then-drag are the same gesture, sharing
-        // the existing sticky-thumb path. Skipping PendingClick and
-        // going straight to Dragging means the first scroll fires on
-        // MouseDown (so a quick click lands the band on the cursor
-        // even without any mouse movement). If there's no band yet
-        // (no file loaded / pre-layout) we bubble instead — nothing
-        // to center on.
+        // Send the scroll request immediately so the band lands at the
+        // cursor, but do NOT set the optimistic ghost band — let the
+        // natural ViewportState propagation paint the band at its
+        // actual settled (line-snapped) position on the next frame.
+        // Using the ghost path here would lock the band visually to
+        // the cursor's exact Y, then snap to the line-snapped position
+        // on MouseUp when the ghost clears — visible as a jiggle on
+        // smaller files where one line of editor scroll spans several
+        // bar pixels. The ghost's value-add is smoothing fast drag
+        // (decoupling the bar paint from editor scroll lag); a
+        // stationary click has nothing to smooth.
+        //
+        // If the user follows up with motion, the first MouseMove
+        // activates the ghost via EmitDragScroll and we're back on
+        // the smooth-drag path. The transition is a small one-time
+        // snap to cursor, masked by the motion that caused it.
+        //
+        // Still go directly into Dragging (skipping PendingClick) so
+        // MouseUp doesn't try to fire a JumpToHunk — there's no hunk
+        // to commit to, and the scroll has already been sent.
         if (idx < 0 && !inBand)
         {
             if (band is null) return;
@@ -382,7 +393,9 @@ protected override void OnMouseLeftButtonDown(MouseButtonEventArgs e)
             _interaction = BarInteractionState.Dragging;
             ToolTip = null;
             CaptureMouse();
-            EmitDragScroll(p);
+            double targetBandTopY = p.Y - _bandDragOffsetFromTop;
+            double fraction = ActualHeight <= 0 ? 0 : targetBandTopY / ActualHeight;
+            _vm.RequestScrollByVerticalFraction(fraction);
             e.Handled = true;
             return;
         }