State the compatibility baseline and the channels

NFR-COMPAT-1 and NFR-COMPAT-2 were instructions to write a requirement,
not requirements: "state the API level", "state the channels". Both
are now stated from what the build enforces and what exists.

The baseline is minSdk 28 / targetSdk 36 from the Android Dockerfile,
a Vulkan adapter at wgpu's default limits because compute needs storage
textures — device_from already called that the floor and is tagged for
it — with no optional feature required, since the f16 in FR-DEV-2 is a
texture format and not shader arithmetic. The reference device is the
HONOR ROD2-W09 the figures are taken on, and the second-vendor clause is
recorded as unmet rather than quietly dropped: there is no Mali or
PowerVR device, so an Android figure here is an Adreno figure.

The channels are all self-distribution — Arch package, local Flatpak,
sideloaded APK, NSIS installer — because D13's face weights rule out
every store, and the two consequences are written down: SAF stays
although a sideloaded build need not have it, and S11 becomes a
pre-publication step.

core/dr-gpu/src/lib.rs

@@ -281,6 +281,7 @@ impl GpuContext {
         )))
     }
 
+    /// TRACES: NFR-COMPAT-1
     /// Ask one adapter for a device, with the limits the pipeline needs.
     async fn device_from(adapter: &wgpu::Adapter) -> Result<(wgpu::Device, wgpu::Queue), GpuError> {
         adapter