gpu: Capturer::on_device and Renderer::report

A capturer on a device already open (the app's), and the renderer's
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Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UhhZMBTviDQxZvwnyP89fo

crates/gpu/Cargo.toml

@@ -13,6 +13,7 @@ fieldcraft-render = { workspace = true }
 wgpu = { workspace = true }
 log = { workspace = true }
 thiserror = { workspace = true }
+serde_json = { workspace = true }
 
 [target.'cfg(not(target_arch = "wasm32"))'.dependencies]
 pollster = { workspace = true }