fix(client): address PR #22 review — 3 critical bugs, 2 warnings, 8 suggestions

Critical fixes:
- fog_state: guard _compute_bounds() against all-invalid tiles (negative Rect2i crash)
- fog_shader: read Camera2D zoom dynamically instead of hardcoded Vector2(2,2)
- world_radial: set custom_minimum_size in _ready() from spoke geometry

Warnings:
- fog.gdshader: tighten PERIPHERAL_LOW 0.15→0.55 to match D-059 peripheral band
- Extract color_for_entity_kind() to Constants.gd, decouple CursorRenderer from EntityRenderer

Documentation: shallow copy assumption, gradual decay TODO, tween guard rationale,
fade timing rationale, ToggleInsert TODO, monologue consume-once, hover offset safety,
v6 fixture gap TODO.

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

client/scripts/rendering/cursor_renderer.gd

@@ -128,7 +128,7 @@ func _find_nearest_entity() -> Dictionary:
 			best_dist = dist
 			result.id = entity.entity_id
 			result.kind = entity.get("kind", {}).get("variant", "")
-			result.color = EntityRenderer._color_for_kind(entity)
+			result.color = Constants.color_for_entity_kind(entity)
 			result.offset = (xform * center) - mouse_screen
 	return result
 
@@ -191,6 +191,11 @@ func _interpolate() -> void:
 # --- Drawing ---
 
 func _draw() -> void:
+	# _hover_offset is computed in _detect_hover() during _process(), not recalculated
+	# here. This is safe because Camera2D (tree sibling, earlier in scene order) applies
+	# its smoothing transform before CursorRenderer._process() reads canvas_transform.
+	# Nothing modifies the canvas transform between _process() and _draw().
+
 	# Bloom pass — wider, semi-transparent glow
 	if _bloom > 0.01:
 		var bloom_mod := 1.0