Revert ab29ec8: container==content auto-fit made it worse — back to alpha-crop with the container at element size

The container tracks the element's own Width/Height again; the crop stays in the bitmap.

TASKS.md

@@ -917,19 +917,16 @@ capturing the primary display (which causes the infinity mirror effect).
 8. ✅ Preview shows live web content (not just a blank rectangle)
 9. ☐ Handle navigation errors, invalid URIs, timeout gracefully
 
-**Rendering model (2026-08-28, canvas-size viewport + alpha crop + CONTAINER==CONTENT):**
+**Rendering model (2026-08-28, canvas-size viewport + ALPHA-BBOX crop):**
 the page renders at the MASTER CANVAS size (1920×1080), stable, never tracked (no reflow/truncation;
 scrollbars suppressed via `overflow:hidden`). `FindContentBounds` scans the Bgra32 capture and crops
 to the bounding box of non-transparent pixels — the widget's true rendered extent, measured from the
-frame itself (NO DOM query, immune to layout timing, can never truncate content; full-canvas widgets
-fall through to the full frame). `ContentCanvasSize` maps the cropped pixel rect to canvas units
-(DPI-correct); `MainViewModel.OnWebView2PreviewBitmapChanged` sizes the element's Width/Height to it —
-so the element grid AND the SelectionOverlay (both bound to the element's Width/Height) equal the
-widget exactly. Auto-fit suppressed while dragging (`IsPreviewDragging`). `Stretch="Fill"` is now
-~1:1; no cropped bitmap is stretched into a larger frame.
-⚠️ Lesson bank: never return `JSON.stringify` from `ExecuteScriptAsync` (double-encodes); never
-measure DOM on NavigationCompleted (unsettled layout broke the image — `a5b9952`); fixing the
-bitmap crop without sizing the container leaves the gap (— `bccdb48`).
+frame itself (NO DOM query, immune to layout timing; can never truncate content; full-canvas widgets
+fall through to the full frame = prior verified-good image). `Stretch="Fill"` maps the cropped frame
+flush under the selection box → box hugs the widget on all four sides. `QueryContentBoundsAsync` +
+the JS content-bounds script are DELETED. ⚠️ Lesson bank: never return `JSON.stringify` from
+`ExecuteScriptAsync` (double-encodes); never measure DOM stuff on NavigationCompleted (unsettled
+layout broke the image — `a5b9952`); measure rendered pixels instead.
 
 **Properties panel (2026-08-28):** web URI ✓/✕ icon buttons are `IsTabStop="False"` so Tab flows
 X→Y→W→H→URI; the ✕ button now clears the URI textbox (was reverting to the pre-accept snapshot).