RHI vulkan updates

AGENTS.md

@@ -36,6 +36,16 @@ All code follows the patterns established in `src/wapp/`. The project prefix is
 
 - **Tabs for indentation**, 8-column tab width.
 - **Braces** on the same line as control statements (Attach style).
+- **Braces on single-line if statements**: Always use braces, even for single-line bodies:
+  ```c
+  // correct
+  if (!buffer) { return; }
+  if (!texture) { _abort("alloc failed"); }
+
+  // wrong
+  if (!buffer) return;
+  if (!texture) _abort("alloc failed");
+  ```
 - **Pointers**: `*` against the name, not the type (`PrRhiBuffer *buf`, not `PrRhiBuffer* buf`).
 - **Line width**: 120 columns.
 - **Continuation lines** align to the opening parenthesis.
@@ -117,6 +127,24 @@ prefer SoA layouts, batch processing, and minimise pointer chasing. Keep
 the DAG in contiguous arrays (e.g. adjacency lists packed in flat buffers)
 rather than individually allocated linked structures.
 
+### Frame-by-frame command batching
+
+Commands that execute every frame must avoid arena allocation. Use stack
+arrays with a while-loop to batch operations in fixed-size chunks:
+
+```c
+while (count > 0) {
+	VkTypeArray batch = wpArrayWithCapacity(VkType, 16, WP_ARRAY_INIT_FILLED);
+	u32 batch_size = count < wpArrayCapacity(batch) ? count : (u32)wpArrayCapacity(batch);
+	// ... process batch ...
+	vkCmd*(cb->handle, ...);
+	count -= batch_size;
+	first += batch_size;
+}
+```
+
+This avoids per-frame arena churn while handling arbitrarily large inputs.
+
 ### Graph / adjacency lists
 
 Adjacency list nodes must be **separately allocated from the vertex array**.