Client: size canvas to viewport, 100% zoom, patch blit no longer clears the screen

README.md

@@ -80,8 +80,13 @@ v3 instead:
 4. **Binary frames.** `[MAGIC][type][u32 hlen][json][webp]` — no base64 (+33%
    removal), no JSON-wrapping of image data.
 5. **Zero CDN / zero framework.** `index.html` is ~7.8 KB, no external requests.
-6. **Async refinement.** Window content is generated off the input critical path.
-7. **A blocking `Queue.get()`** replaces the old 50 ms busy-wait poll.
+6. **100% adaptive viewport.** The canvas backing store is sized to the viewport
+   at startup and the framebuffer is drawn at **100% zoom** (one fb pixel per CSS
+   pixel); it only shrinks to fit a smaller window, never magnifies. Partial
+   patches repaint **only** their own region, so the rest of the desktop stays
+   intact (the earlier `blit` cleared the whole canvas on every patch).
+7. **Async refinement.** Window content is generated off the input critical path.
+8. **A blocking `Queue.get()`** replaces the old 50 ms busy-wait poll.
 
 Measured (see below): interaction cost is a `LayerStack` build of **~0.15 ms**
 and a **~1.9 ms** frame, with **0 cache misses** once warm.