✨ show forester planting radius preview while placing hut (Issue #47)

Semi-transparent green 11x11 tile overlay follows the ghost cursor
when forester_hut is selected. Disappears on deactivate/cancel.

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

CHANGELOG.md

@@ -8,6 +8,7 @@ Format follows [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 ## [Unreleased]
 
 ### Added
+- **Forester Radius Preview** (Issue #47): When placing a Forester Hut, a semi-transparent green overlay shows the full planting zone radius (Chebyshev 5 = 11×11 tiles) following the ghost cursor; disappears on cancel
 - **Demolish Mode** (Issue #50): New 💥 Demolish button in the action bar; hover shows a red ghost over any building with a refund percentage; buildings demolished within 3 minutes return 100% of costs (linear decay to 0%); mine footprint tiles are unblocked on teardown; Nisse working inside a demolished building are rescued and resume idle; tile types are restored where applicable (floor/wall/chest → grass)
 - **Mine Building** (Issue #42): 3×2 building placeable only on resource-free ROCK tiles (costs: 200 wood + 50 stone); Nisse with mine priority walk to the entrance, disappear inside for 15 s, then reappear carrying 2 stone; up to 3 Nisse work simultaneously; ⛏ X/3 status label shown directly on the building in world space; surface rock harvesting remains functional alongside the building