Draw the whole 3D view in place of the client's renderer

The full view is now the default. While the renderer process covers the whole
view (Channel::covering, set after each frame it presents), the adapter skips
the client's renderer's clears and draws, decided per frame; the client's
renderer still gets state and resources, and draws again as soon as the
renderer process stops covering the view.

The client's window no longer gets WS_CLIPCHILDREN: the client draws when its
window gets WM_PAINT, which a window entirely covered by clipped children never
gets (it fell to about one frame a second). The flip model swap chain shows
above the client's drawing anyway.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

docs/architecture.md

@@ -29,19 +29,25 @@ creates (each 3D view, and again on room changes), the adapter:
 
 The renderer process draws into a child window it creates inside the client's window: window handles are valid in
 every process, and Windows allows child windows across processes (Chrome's GPU process works this way). The child
-is disabled so mouse input goes to the client's window under it, and the adapter gives the client's window
-`WS_CLIPCHILDREN` so the client's own drawing stays out of it. The process exits when the engine is destroyed or the
-client exits.
+is disabled so mouse input goes to the client's window under it. Its swap chain is a flip model one, which the
+compositor shows above the client's own drawing. The client's window must not clip its children (`WS_CLIPCHILDREN`):
+the client draws a frame when its window gets `WM_PAINT` (`SceneWindow.dll` invalidates it, and draws on the paint),
+and a window entirely covered by clipped children never gets one, so the client fell to about one frame a second.
+The process exits when the engine is destroyed or the client exits.
 
 ## Status
 
-The renderer process draws the client's whole scene, over the right half of the 3D view, beside the client's own
-Direct3D renderer on the left (the adapter still forwards everything to it). Checked in rooms with screenshots of
-both renderers side by side (the compare view): they match, particles and the 2D overlay (name tags) included.
+The renderer process draws the whole 3D view in place of the client's renderer (the full view, the default). The
+adapter still forwards everything to the client's Direct3D renderer (state and resources: it draws render targets and
+reads textures back, which the renderer process doesn't yet), but while the renderer process covers the whole view
+(`Channel::covering`, set after each frame it presents) the client's renderer skips its clears and draws, decided per
+frame; it draws again as soon as the renderer process stops covering the view (the view changes, or the process
+fails). Checked in rooms with screenshots of both renderers side by side (the compare view): they match, particles
+and the 2D overlay (name tags) included.
 
 For comparing while the client runs (development):
 
-- Views: `T5DE_RENDERER_VIEW` (off, split, full or compare) when the client starts, or
+- Views: `T5DE_RENDERER_VIEW` (off, split, full (the default) or compare) when the client starts, or
   `%TEMP%\t5de-renderer-view.txt` holding one of those at any time. Compare draws the left half's scene over the
   right half, so both renderers show the same thing side by side.
 - `%TEMP%\t5de-renderer-shaders\fixed_function.hlsl`, if present, replaces the built-in shaders and is reloaded
@@ -63,8 +69,8 @@ For comparing while the client runs (development):
   the right half visibly trails, mostly from compositing another process's window over Remote Desktop. The
   renderer process draws only the newest frame when it falls behind, and keeps at most one frame queued.
 
-Next: render targets (offscreen frames are skipped), the renderer process drawing the whole view in place of the
-client's renderer, and one renderer process for all of a client's views.
+Next: render targets (offscreen frames are skipped, and drawn by the client's renderer), and one renderer process for
+all of a client's views.
 
 ## Building