feat(agent): add safe lowlevel extension point

adk-rust/crates/awatch-agent-rs/src/lowlevel/mod.rs

@@ -0,0 +1,18 @@
+//! Safe low-level extension point for future agent optimizations.
+//!
+//! The default implementation is pure Rust. The `asm-lowlevel` feature is a
+//! reserved integration point for future platform-specific CPU and timing
+//! probes implemented through `core::arch`, inline assembly, or native OS
+//! calls. Keep any future `unsafe` code isolated inside this module.
+
+pub mod cpu;
+pub mod timing;
+
+pub use cpu::{CpuFeatures, get_cpu_features};
+pub use timing::{high_precision_time_ns, monotonic_ticks};
+
+#[cfg(feature = "asm-lowlevel")]
+pub const LOWLEVEL_BACKEND: &str = "asm-lowlevel-ready-rust-fallback";
+
+#[cfg(not(feature = "asm-lowlevel"))]
+pub const LOWLEVEL_BACKEND: &str = "rust";