Windows: a maximized window stops a pixel short of an auto-hidden taskbar

An auto-hidden taskbar reserves no work area, so the guard that keeps
the custom title bar's window borderless left a maximize covering the
whole monitor. The shell treats a caption-less window that covers its
monitor as a full-screen app, and in PhotoCraft, which has the same
guard, the hidden taskbar then did not show when the pointer reached
its edge (storytold/photocraft#4845).

While a maximized window covers its whole monitor, the guard now finds
the taskbars (the Shell_TrayWnd and Shell_SecondaryTrayWnd windows),
takes the monitor edge nearest each one's center, and stops the window
one pixel short of the monitor on each of those edges where the work
area reaches the monitor's edge. A taskbar that reserves a work area
is still cleared by the move into the work area. This ports
Higgs32584's fix in PhotoCraft (storytold/photocraft#6878).

Docs: docs/target-app-parity.md.

Co-authored-by: Higgs32584 <mhiggins217@gmail.com>

docs/target-app-parity.md

@@ -612,6 +612,7 @@ Moved from the ROADMAP's "Shipped so far" on 2026-10-10. Update it when a featur
   - Shortcut sets other apps save as text (`.kys`) open in Import Shortcut Set from File › Open, from Edit › Keyboard Shortcuts › Import… in the desktop app, or from a drop on the window. It matches each entry to a tool, command or panel by name and decodes the file's key and modifier codes where VectorCraft's default shortcuts agree on them; the user answers the rest, and Apply fills the Keyboard Shortcuts dialog's working set. The answers are kept with the preferences for the next import (`shortcutSet.read`, `importMatches.*`).
   - On Windows and Linux the app bar is the window's title bar (its own minimize, maximize and close buttons, drag to move, edges to resize), with the dragon app icon as the brand mark; dialogs and menus size to their content. As on a native menu bar, once one menu is open, moving the pointer onto another title opens that one.
   - On Windows a maximized window stays inside the work area with the taskbar on any edge (#3242, #3723).
+  - On Windows a maximized window stops one pixel short of each monitor edge where an auto-hidden taskbar sits.
 - **Tools:**
   - **Shaper:** uneven squares and rectangles become live rectangles even when drawing begins mid-edge. Recognition uses uniformly spaced samples and closed-loop corners, fits rectangle edges/angles rather than requiring a nearly perfect bounding-box fill, and includes the pointer-release position. Rectangles/squares and ellipses snap to 45° steps, hexagons to 90°, and triangles point up or down; lines keep their free angle even with Shift. Shaper Groups retain the live originals, merge regions with the gesture-origin fill, punch fills independently from strokes, remove boundaries on exiting scribbles and trim protruding stroke pieces. Source moves/resizes re-evaluate the result in the same undo step; double-click enters construction editing, and with the Shaper or Selection tool a click on the arrow widget beside a Shaper Group's original shapes switches the group between Face Selection and Construction mode. Native save/reopen, face recoloring, Release and Expand are covered. Finer gesture heuristics remain.
   - **Selection:** Selection, Direct/Group Selection, Magic Wand, Lasso. A Shift-drag marquee toggles what it reaches: objects with the Selection tool, anchors with Direct and Group Selection (#483); the Lasso adds with Shift and subtracts with Alt. Dragging a path segment with Direct Selection bends it when it's curved (its anchors stay) and moves its two anchors when it's straight, one undo step; the fill, Shift or Alt still pick the whole path (Alt-drag copies it).