Add vegetation ignition risk checks

Docs/TechnicalDesignDocument.md

@@ -345,6 +345,14 @@ when excessive fuel is burning, and is reduced by maintenance, cleared area,
 containment, and wet weather. This first risk layer does not yet ignite nearby
 vegetation or structures; later 0.1.P items consume the replicated risk score.
 
+Grass and forest ignition checks consume that risk score. Campfires query
+`AAgrarianFoliagePatch` for nearby grass, shrub, and tree instance counts inside
+`VegetationIgnitionCheckRadius`. Unsafe placement near dry fuel accumulates
+separate replicated grass/brush and forest ignition risk, adjusted by burn
+duration, wind speed, current weather, cleared-area maintenance, and the
+campfire's current risk ratio. Reaching the threshold marks the relevant
+ignition flag, while later spread rules decide how active fires propagate.
+
 Campfires expose native extinguish logic through `AAgrarianCampfire::Extinguish`.
 Extinguishing clears remaining fuel, turns off replicated lit state, and reuses
 the same visual update path as natural fuel depletion.