Initial commit: xenia-rs workspace for Xbox 360 RE

Rust reimplementation of the xenia Xbox 360 emulator targeting reverse-
engineering and preservation, initially scoped to Project Sylpheed.

Includes:
- XEX2 loader (LZX decompression, AES decryption, PE parsing)
- XISO / XGD2 disc image VFS
- PPC interpreter with 200+ opcodes and VMX128 decoding
- Static analyzer: functions, cross-references, labels, asm + SQLite output
- HLE kernel covering the xboxkrnl/xam subset used by Sylpheed init
- Debugger with in-memory and SQLite-backed execution tracing
- `xenia-rs` CLI with extract/dis/exec commands that produce cumulative,
  superset SQLite databases and opt-in instruction/import/branch traces

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

crates/xenia-gpu/src/command_processor.rs

@@ -0,0 +1,17 @@
+/// PM4 command processor stub.
+/// Will parse the GPU command ring buffer and dispatch to render operations.
+pub struct CommandProcessor {
+    pub enabled: bool,
+}
+
+impl CommandProcessor {
+    pub fn new() -> Self {
+        Self { enabled: false }
+    }
+}
+
+impl Default for CommandProcessor {
+    fn default() -> Self {
+        Self::new()
+    }
+}

crates/xenia-gpu/src/lib.rs

@@ -0,0 +1,21 @@
+pub mod command_processor;
+pub mod register_file;
+
+/// 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()
+    }
+}

crates/xenia-gpu/src/register_file.rs

@@ -0,0 +1,28 @@
+/// Xenos GPU register file. 0x6000 32-bit registers.
+pub struct RegisterFile {
+    pub regs: Vec<u32>,
+}
+
+impl RegisterFile {
+    pub fn new() -> Self {
+        Self {
+            regs: vec![0u32; 0x6000],
+        }
+    }
+
+    pub fn read(&self, index: u32) -> u32 {
+        self.regs.get(index as usize).copied().unwrap_or(0)
+    }
+
+    pub fn write(&mut self, index: u32, value: u32) {
+        if let Some(r) = self.regs.get_mut(index as usize) {
+            *r = value;
+        }
+    }
+}
+
+impl Default for RegisterFile {
+    fn default() -> Self {
+        Self::new()
+    }
+}