Web source: geometry-agnostic viewport==box model — viewport locked to element box, Stretch=Fill, no dead space

TASKS.md

@@ -917,18 +917,15 @@ 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, the fix that works):** WebView2 viewport is FIXED at the master
-canvas size (1920×1080) in `Register`, never tracking the element box — the OBS/CEF pattern
-(fixed render viewport, display box scaled independently via `Stretch="Uniform"`). Capturing the
-box-sized viewport was the truncation bug. Display `Stretch`: web → `Uniform` (no crop),
-everything else → `UniformToFill`. Graceful-error handling (item 9) is a follow-up.
-
-**Box-vs-content padding (2026-08-28):** whitespace gaps between the bounding box and the web
-content were the page's own UA margins/padding + body sizing to content instead of the viewport.
-Fixed by injecting a CSS reset into every document via
-`CoreWebView2.AddScriptToExecuteOnDocumentCreatedAsync` (margin/padding 0, html/body 100% of
-viewport, overflow hidden, transparent bg) and anchoring the web `<Image>` at (0,0)
-(`HorizontalAlignment/VerticalAlignment=Left/Top`) inside the element box.
+**Rendering model (2026-08-28, geometry-agnostic — supersedes the earlier fixed-viewport model):**
+the WebView2 viewport IS the element box (`Source.Width × Source.Height`); the page renders at
+exactly the box size and the captured frame is displayed with `Stretch="Fill"`, so the selection
+rect always bounds the actual rendered content — no fixed render size, no aspect assumptions,
+no dead space/padding for any widget geometry. A `PropertyChanged` hook keeps the viewport
+locked to the box; capture is re-triggered on resize. Graceful-error handling (item 9) is a
+follow-up. Earlier attempts for the record: (a) fixed 1920×1080 viewport + `Stretch="Uniform"`
+fixed the truncation but left box-vs-content gaps (box aspect ≠ capture aspect); (b) CSS reset
+injection made gaps larger (belayed by creator).
 
 ### Design decisions