xenia-gpu: end-to-end Xenos pipeline (PM4, ucode, EDRAM, resolve)

First real GPU implementation. Ring/PM4 frontend (ring_view,
ring_drain, pm4) drains the command processor; gpu_system owns the
threaded backend (DrainFence RPC + parker/fence helpers from M1) and
the MMIO-mapped register block (mmio_region).

Xenos shader frontend: ucode/{alu,control_flow,fetch,mod}.rs decode
the Xbox 360 microcode, translator.rs lowers it onto the WGSL
xenos_interp interpreter shader (shaders/xenos_interp.wgsl).
shader_metrics.rs counts decode/translate work.

Render state: draw_state, primitive, render_target_cache,
texture_cache, tiled_address (Xenos's swizzled tiled-memory layout),
xenos_constants (register field constants), edram (the 10 MiB EDRAM
model with MSAA), and resolve.rs (TILE_FLUSH copy-out — clear-resolve
plus bitwise-equivalent 32 bpp + 64 bpp paths landed). handle.rs
owns the typed GPU-resource handles the kernel hands out.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/xenia-gpu/src/lib.rs

@@ -1,21 +1,49 @@
+//! Xenos GPU emulation for xenia-rs.
+//!
+//! Modules:
+//! - [`pm4`]: packet format decoder + Type-3 opcode set.
+//! - [`ring_view`]: ring-buffer bookkeeping (base/size/read/write pointers).
+//! - [`register_file`]: 0x6000-entry register array backing the CP + state.
+//! - [`gpu_system`]: top-level `GpuSystem` + PM4 executor running one packet
+//!   per call (see the plan's P2 for the design rationale).
+//!
+//! Legacy module `ring_drain` and `command_processor` are retained while P3+
+//! migrations finish; they will be removed once every caller is on
+//! [`gpu_system::GpuSystem`].
+
 pub mod command_processor;
+pub mod draw_state;
+pub mod edram;
+pub mod gpu_system;
+pub mod handle;
+pub mod mmio_region;
+pub mod pm4;
+pub mod primitive;
 pub mod register_file;
+pub mod ring_drain;
+pub mod ring_view;
+pub mod render_target_cache;
+pub mod resolve;
+pub mod shader_metrics;
+pub mod shaders;
+pub mod texture_cache;
+pub mod tiled_address;
+pub mod translator;
+pub mod ucode;
+pub mod xenos_constants;
 
-/// Stub GPU system for initial implementation.
-pub struct GpuSystem {
-    pub register_file: register_file::RegisterFile,
-}
-
-impl GpuSystem {
-    pub fn new() -> Self {
-        Self {
-            register_file: register_file::RegisterFile::new(),
-        }
-    }
-}
-
-impl Default for GpuSystem {
-    fn default() -> Self {
-        Self::new()
-    }
-}
+pub use gpu_system::{
+    ExecOutcome, GpuBlock, GpuMmio, GpuStats, GpuSystem, InterruptSource, PendingInterrupt,
+    ShaderBlob, SwapNotification, WaitCmp,
+};
+pub use handle::{
+    DrainReply, GpuBackend, GpuCommand, GpuDigestSnapshot, GpuHandle, GpuWorker,
+    shutdown_and_join_with_timeout, spawn_gpu_worker, spawn_noop_worker,
+};
+pub use mmio_region::build_region as build_mmio_region;
+pub use pm4::{
+    PacketHeader, PacketKind, PM4_INTERRUPT, PM4_NOP, PM4_XE_SWAP, SWAP_SIGNATURE,
+    type3_opcode_name,
+};
+pub use ring_drain::{DrainResult, drain};
+pub use ring_view::RingBufferView;