fix(ui): stop clipping the last log line in scrollable output

Avalonia 12 leaves ScrollViewer.Padding out of the scroll Extent, so at
maximum offset the content still overhangs the viewport by the padding
height — the last lines were cut off and unreachable even after
ScrollToEnd(). Move the inset onto the content (Margin on the inner
ItemsControl/StackPanel) and leave the ScrollViewer padding-free.

Affects the work console Output/Git/Session tabs, the reusable session
terminal (task + prep log) and the log visualizer.

src/ClaudeDo.Ui/CLAUDE.md

@@ -111,6 +111,7 @@ snaps `CanResize="True"` windows, which is the opt-in), and it insets itself by
 
 - **`PathIcon` *fills* its geometry.** Line-art/stroke icons must be authored as filled geometry or rendered with a stroked `Path` (e.g. `Icon.PlanDay` via the `Path.plan-icon` style). A pure stroke path in a `PathIcon` is **invisible**.
 - **`NumericUpDown.Value` is `decimal?` and goes null while the box is empty** — i.e. every time the user clears a value to type a new one. Bound TwoWay to a non-nullable `int`/`decimal`, that null throws `InvalidCastException`. Either bind a `decimal?` property (as `AgentConfigEditorViewModel.MaxTurns` does) or add `Converter={StaticResource KeepLastNumber}`, which drops the null via `BindingOperations.DoNothing`.
+- **`ScrollViewer.Padding` is excluded from the Extent (Avalonia 12).** At max scroll the content still sticks out below the viewport by the padding height, so the last line(s) are clipped and unreachable — even after `ScrollToEnd()`. Put the inset on the *content* (`Margin` on the inner `ItemsControl`/`StackPanel`) instead. Verified headlessly: 12,8,12,4 on the viewer → last item 20px below the viewport; same inset as content margin → fully visible.
 - **Never bind bare punctuation gestures.** Window key bindings live on `MainWindow` (`Ctrl+K` search, `Ctrl+N` add-task). `OemQuestion` once held search focus and silently swallowed `#` app-wide on a German layout.
 - **`FocusClearing`'s Escape handler is scoped to `MainWindow`** (`AddClassHandler<MainWindow>`, not `<TopLevel>`) — it clears focus from a TextBox on Escape, mirroring click-outside. Modals are separate `Window` instances that bind their own Escape → close, so it never runs there. Mission Control's ConPTY tiles are in `MissionControlWindow`, also unaffected, so **Escape always reaches the PTY**.
 - **Review gate:** Approve & Merge stays disabled until the diff has been opened once, and re-locks per run → [review-merge](../../docs/explore-notes/review-merge.md).