Hide window-link graphs in split view; fix left-edge drag-out dead zone

[epeicher]

Follow-up to #337.

CleanShot.2026-07-14.at.18.33.17.mp4

What it does

Two fixes for window links (#337) interacting with split view:

1. Graphs hide in split view. Windows snapped into a half-screen tile (snapped-left / snapped-right) no longer draw relation ties. The ties come back the moment a window is dragged back out to floating.
2. The left window can be dragged out of split view. Dragging a snapped-left window's title bar now moves it with the cursor from the first pixel, same as the right window always did.

Rationale

Graphs. With two related windows tiled side-by-side, a spline's natural anchors sit on the split seam — which the partner window covers. The occlusion-aware anchoring then fell back to the only visible border stretch, the screen edge, and drew an artifact spline from the edge of the desktop across the snapped window's content. A half-screen tile has no free border to anchor on: any tie either crosses the partner or re-anchors on the screen edge — noise, not information.

Drag. commitUnstate re-anchors an un-snapping window under the cursor at cursorX - savedWidth × grabRatio. For a snapped-left window whose saved floating width exceeds the half-screen (the default 1200 px window vs a ~770 px half), that anchor is negative. The drag offsets derived from the unclamped value, but the move loop clamps x ≥ 0 — so the window stayed pinned at the left edge (sliding only vertically) until the cursor traveled the entire overshoot, ~200 px+. Snapped-right windows never produce a negative anchor, which is why only the left side felt broken.

Implementation

• src/window-links/render-host.ts: new drawableRectOf() — snapped windows contribute null rects to edges and group members, the same not-drawable signal minimized windows already send (renderers skip null-endpoint edges per the existing contract). They stay in obstacles: a half-screen tile still occludes other windows' borders. The frame pipeline also subscribes to SNAP_ZONE_COMMITTED / SNAP_SPLIT_FILLED — snap geometry lands after the drag session ends, so without them the last drag frame went stale.
• src/window/pointer.ts: commitUnstate clamps the re-anchor left/top to EDGE_MARGIN, the same lower bound the move loop enforces, so the drag offset matches the geometry actually written and the window tracks the cursor 1:1 immediately.
• Contract docs (src/window-links/types.ts, docs/javascript-reference.md, docs/examples/window-links.md): the null-rect semantics now list split view alongside minimized / other-desktop.

Testing instructions

npm run test:js -- drag-unstate window-links-render-host

Both new regression tests fail on trunk and pass here.

Manual (wp-env, two related windows — e.g. a post editor and one of its comments):

1. With both windows floating, confirm the spline draws between them.
2. Drag one to the left edge to snap it; pick the other in the split overview. No spline should draw while tiled.
3. Grab the left window's title bar mid-bar and drag right a short distance — the window must follow the cursor immediately instead of sticking to the edge.
4. Once both windows float again, the spline reappears.