feat(wind): Level 2 — canvas particle simulation (uniform field)

- ParticleWindView: transparent View overlay on the map; tracks 300 particles
  as three FloatArrays (lat, lon, age) — no per-frame allocation; projects
  lat/lon → screen via MapLibreMap.projection each frame; draws a 14px tail
  segment in the wind travel direction with alpha fading by age; respawns
  out-of-bounds/aged particles randomly within visible bounds; speed scaled
  to viewport so animation is consistent at any zoom level; animates via
  postInvalidateOnAnimation()
- activity_main.xml: ParticleWindView added above MapView, match_parent,
  non-interactive (clickable/focusable=false)
- MainActivity: finds particle_wind_view; calls attachMap after getMapAsync;
  feeds directionDeg/speedKt from windArrow StateFlow

https://claude.ai/code/session_01HXPjBsogsJVRwCiekDGkJX

1 files changed, 7 insertions, 0 deletions

diff --git a/android-app/app/src/main/res/layout/activity_main.xml b/android-app/app/src/main/res/layout/activity_main.xml
index 68abc60..feeb43d 100644
--- a/android-app/app/src/main/res/layout/activity_main.xml
+++ b/android-app/app/src/main/res/layout/activity_main.xml
@@ -17,6 +17,13 @@
             android:layout_width="match_parent"
             android:layout_height="match_parent" />
 
+        <org.terst.nav.ui.map.ParticleWindView
+            android:id="@+id/particle_wind_view"
+            android:layout_width="match_parent"
+            android:layout_height="match_parent"
+            android:clickable="false"
+            android:focusable="false" />
+
         <!-- Overlay Fragment Container (for Log, Safety, Help) -->
         <FrameLayout
             android:id="@+id/fragment_container"