docs: add ASCII diagram of GPU init chain to S3

docs/01-rainbow-triangle.md

@@ -192,6 +192,18 @@ exits.
 
 New concept: **5-layer GPU connection.** Each layer adds a capability:
 
+```text
+Instance
+   │
+   ├──> Surface          (winit window → GPU surface)
+   │
+   ├──> Adapter          (select GPU: integrated vs discrete)
+   │
+   ├──> Device + Queue   (GPU connection + command submission)
+   │
+   └──> SurfaceConfiguration (swapchain: format, size, present mode)
+```
+
 1. **[Instance](concepts/GLOSSARY.md#instance)** — opens a connection to the
    graphics driver. On Vulkan this loads the Vulkan loader and registers
    instance-level extensions. On WebGL this picks the browser GPU context.
@@ -935,6 +947,19 @@ continues the next frame while the GPU works in the background.
 > `encoder.finish()` seals the script. `queue.submit()` dispatches it. The GPU
 > executes it later, in parallel. There is no `.await` on a draw call.
 
+### Render Loop Cycle
+
+```
+[RedrawRequested event]
+         │
+         ▼
+get_current_texture() → [Success?] → Yes → record commands
+         │                                        │
+         └── No (Timeout/Occluded) → skip frame    │
+                                                    ▼
+device.poll() → encoder.begin_render_pass() → draw() → submit() → present()
+```
+
 ### The `render(&mut self)` Method Signature
 
 ```rust