feat(simulation): add server/src/atlas/ — full Phase 1 generation pipeline

Ten-module atlas package implementing the D-194–D-218 district generation
stack: heightmap loader, BodyWorldState LRU cache, D8 drainage routing,
background generation queue, five-phase attractor-matching, three-component
district mix, block irregularity, tile condition thresholds, and the Phase 1
skeleton generator that wires them into DistrictSkeleton.

Closes #916 #917 #918 #919 #920 #922 #923 #924 #899.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

server/src/atlas/mod.rs

@@ -0,0 +1,14 @@
+//! Atlas data loaders — reads pre-computed build-time data from systems.db.
+//!
+//! These loaders are used by the runtime-background tier (D-200, D-206) when
+//! populating BodyWorldState (D-203). They are never called on the main tick thread.
+
+pub mod attractor_matching;
+pub mod block_irregularity;
+pub mod body_world_state;
+pub mod district_mix;
+pub mod drainage;
+pub mod gen_queue;
+pub mod heightmap;
+pub mod skeleton_gen;
+pub mod tile_condition;