Update SLAM module documentation

Replace placeholder comment with accurate description of the
implemented occupancy grid and particle filter functionality.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: Jonathan D.A. Jewell

src/rust/src/slam.rs

@@ -1,6 +1,7 @@
 //! SLAM (Simultaneous Localization and Mapping) implementation
 //!
-//! Placeholder for future SLAM implementation
+//! Provides occupancy grid mapping and particle filter localization
+//! for robot vacuum navigation and positioning.
 
 use crate::types::Pose;
 use ndarray::Array2;