Render continuously and optimize the glTF viewer

Remove vsync and dirty-flag frame gating, optimize PBR sampling and lighting, add a direct-to-canvas loadout, and preserve camera state on viewer resize.

Add regression coverage and update rendering documentation.

Amp-Thread-ID: https://ampcode.com/threads/T-01a0b382-1e79-712b-abd1-d29201c9bb5e
Co-authored-by: Heaust Azure <heaust.azure@gmail.com>

coredocs/index.md

@@ -15,7 +15,7 @@ features:
   - title: Raw transport
     details: Start core/worker.js, correlate replies, and handle profiler events.
   - title: Shared rows
-    details: Build typed views, allocate slots, and follow the dirty-lane protocol.
+    details: Build typed views, allocate slots, and control continuous rendering.
   - title: Graph wire format
     details: Encode, compile, and activate complete WebGPU render and compute graphs.
 ---
@@ -27,7 +27,7 @@ The browser main thread owns the HTML canvas and starts the module worker. The w
 The application is responsible for three important contracts:
 
 1. Correlate each reply by its `request` value; profiler messages are unsolicited.
-2. Finish shared-memory writes before setting `signals[5]` (`sabDirty`).
+2. Shared-memory value edits are rendered continuously; no `sabDirty` notification is needed. Pause before updates that must not overlap rendering.
 3. Before a mutation that invalidates compiled render bundles, set `signals[6]` (`bundleDirty`), make the mutation, compile and switch a replacement graph, then let successful `switch-loadout` clear lane 6.
 
 This site describes the current wire API, not the higher-level wrapper API.