test(mc-mapgen): relax flaky wall-clock guard in test_map_gen_standard_speed

The 500ms bound had negative headroom on the DO test fleet (s-8vcpu-16gb): standard
mapgen runs ~465-608ms there and drifts higher under the full parallel test pool, so
the test flaked (passed isolated, failed in the 2923-test workspace run). Relaxed to a
generous 2500ms order-of-magnitude regression guard — still catches a real (O(n^2)-class,
seconds) regression without flaking on host/CI load. Verified 5/5 green on the fleet.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/simulator/crates/mc-mapgen/src/lib.rs

@@ -1290,13 +1290,18 @@ mod tests {
 
     #[test]
     fn test_map_gen_standard_speed() {
-        // Standard map must complete in reasonable time (performance regression guard).
+        // Coarse order-of-magnitude regression guard. The bound is deliberately
+        // generous: on the DO test fleet (s-8vcpu-16gb) standard mapgen runs
+        // ~465-608ms, and under the full parallel test pool it drifts higher, so
+        // a tight 500ms wall-clock assertion flaked (negative headroom). A real
+        // regression here would be an accidental O(n^2) — seconds, not ms — which
+        // 2500ms still catches without flaking on host/CI load variance.
         let gen = MapGenerator::new("{}");
         let start = std::time::Instant::now();
         let grid = gen.generate(999, "standard");
         let elapsed = start.elapsed();
         assert_eq!(grid.tiles.len(), (80 * 52) as usize);
-        assert!(elapsed.as_millis() < 500, "standard map gen took {}ms — too slow", elapsed.as_millis());
+        assert!(elapsed.as_millis() < 2500, "standard map gen took {}ms — too slow", elapsed.as_millis());
     }
 
     // ── guarantee_iron_ore_near_starts tests ─────────────────────────────────