Fix: periodic SOI rescan when no crossing found in look-ahead window

- SEARCH_ORBITS increased from 5 to 10
- Added last_scan_end tracking: when sim_time passes the end of the
  current scan window with no crossing pending, automatically rescans
  the next SEARCH_ORBITS ahead
- Title bar now shows 'rescan in Xs' instead of just 'No upcoming SOI
  crossing', making the system's state visible
- Fixes bug #3: asteroid entering SOI undetected because the scan
  window had expired

visual_test.py

@@ -47,7 +47,7 @@ ASTEROID_SUN = OrbitalElements(
     a=380.0, e=0.35, omega=2.5, M0=0.8, epoch=0.0, mu=MU_SUN,
 )
 
-SEARCH_ORBITS = 5
+SEARCH_ORBITS = 10
 
 # ═══════════════════════════════════════════════════════════════
 #  Display
@@ -155,6 +155,7 @@ def main() -> None:
     sun_crossings = find_soi_crossings(
         ASTEROID_SUN, PLANET, SOI_RADIUS, 0.0, window, n_steps=1000,
     )
+    last_scan_end: float = window  # when this scan window expires
     print(f"Found {len(sun_crossings)} SOI crossing(s):")
     for i, (enter, exit_) in enumerate(sun_crossings):
         print(f"  [{i}] enter={enter:.1f}s  (sun-frame)")
@@ -204,6 +205,26 @@ def main() -> None:
         if not paused:
             sim_time += dt * sim_speed
 
+        # ── Periodic rescan when no crossing is pending ──
+        if (not in_soi and soi_enter_time is None
+                and sim_time >= last_scan_end):
+            window = SEARCH_ORBITS * max(asteroid_sun.period, PLANET.period)
+            sun_crossings = find_soi_crossings(
+                asteroid_sun, PLANET, SOI_RADIUS,
+                sim_time + 0.1, sim_time + window, n_steps=1000,
+            )
+            last_scan_end = sim_time + window
+            cross_idx = 0
+            soi_enter_time = sun_crossings[0][0] if sun_crossings else None
+            if sun_crossings:
+                print(f"\n[rescan @ t={sim_time:.0f}s] "
+                      f"found {len(sun_crossings)} crossing(s), "
+                      f"next enter at t={sun_crossings[0][0]:.0f}s")
+            else:
+                print(f"\n[rescan @ t={sim_time:.0f}s] "
+                      f"no crossings in next {window:.0f}s, "
+                      f"will rescan at t={last_scan_end:.0f}s")
+
         # ── SOI state machine ─────────────────────────────
         # Check entry
         if (not in_soi and soi_enter_time is not None
@@ -259,7 +280,9 @@ def main() -> None:
                 asteroid_sun, PLANET, SOI_RADIUS,
                 sim_time + 0.1, sim_time + window, n_steps=1000,
             )
-            print(f"    Re-scanned: found {len(sun_crossings)} future crossing(s)")
+            last_scan_end = sim_time + window
+            print(f"    Re-scanned: found {len(sun_crossings)} future crossing(s) "
+                  f"(window ends at t={last_scan_end:.0f}s)")
             for i, (enter, _) in enumerate(sun_crossings):
                 print(f"      [{i}] enter={enter:.1f}s")
 
@@ -343,7 +366,9 @@ def main() -> None:
             title = (f"SOI entry in {countdown:.1f}s  "
                      f"(crossing {cross_idx + 1}/{len(sun_crossings)})")
         else:
-            title = "No upcoming SOI crossing"
+            rescan_in = last_scan_end - sim_time
+            title = (f"No SOI crossing in window — "
+                     f"rescan in {rescan_in:.0f}s")
         pygame.display.set_caption(title)
 
         # ── HUD ───────────────────────────────────────────