feat(ci): add performance baseline tooling (#499)

Adds `make perf-baseline` — boots the full server plugin stack with
real content, measures 50 ticks (5 warmup), captures per-tick timing,
entity counts, and process RSS. Includes shadowcast benchmarks. Saves
structured JSON to tests/perf/baseline.json for regression detection.
Supports --compare mode (>20% threshold).

First baseline: mean 366µs, p95 526µs (0.5% of D-026 100ms budget).

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

server/Cargo.lock

@@ -978,7 +978,7 @@ dependencies = [
 
 [[package]]
 name = "settled-reach-server"
-version = "0.1.0"
+version = "0.1.9"
 dependencies = [
  "bevy_app",
  "bevy_ecs",