fix(client): address PR #109 review — 6 warnings + 5 suggestions

Star map (W1-W3, S3):
- _process visibility guard + dirty flag (no redraw when hidden/unchanged)
- _system_hash masked to 31-bit positive range
- Extracted _find_nearest_system() shared helper

game_state.gd (W4):
- Inline load() in apply_snapshot() replaces per-tick overhead; safe at
  runtime because script is already in resource cache

Data pipeline (W5-W6):
- Script-relative path resolution via __file__
- --check mode + make check-star-map staleness target

Minor (S1-S2, S5):
- Removed redundant bone_idx assignment
- Simplified double-negative test assertion
- Documented autoload parse-order convention in CLAUDE.md

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

client/ui/star_map.gd

@@ -96,6 +96,7 @@ var _pan_start_offset: Vector2 = Vector2.ZERO
 var _data_loaded: bool = false
 var _insert_active: bool = true
 var _show_edges: bool = false  # toggle edge display
+var _dirty: bool = true        # redraw needed — set by state changes, cleared after _draw
 
 
 func _ready() -> void:
@@ -106,8 +107,11 @@ func _ready() -> void:
 
 
 func _process(_delta: float) -> void:
-	if _insert_active and _data_loaded:
+	if not visible:
+		return
+	if _dirty and _data_loaded:
 		queue_redraw()
+		_dirty = false
 
 
 ## Called from main.gd when insert state changes.
@@ -122,6 +126,8 @@ func set_insert_active(active: bool) -> void:
 ## Toggle visibility (e.g., from a keybind or button).
 func toggle_visible() -> void:
 	visible = not visible
+	if visible:
+		_dirty = true
 
 
 ## Return the currently selected system data, or empty dict.
@@ -259,8 +265,8 @@ func _sector_sort_key(node: Dictionary) -> float:
 
 ## Deterministic float in [-1, 1] from a string key.
 func _system_hash(key: String) -> float:
-	var h: int = key.hash()
-	return fmod(float(h) / 2147483647.0, 1.0) * 2.0 - 1.0
+	var h: int = key.hash() & 0x7FFFFFFF  # mask to 31-bit positive range
+	return float(h) / 2147483647.0 * 2.0 - 1.0
 
 
 # =============================================================================
@@ -465,9 +471,15 @@ func _gui_input(event: InputEvent) -> void:
 					_pan_start = mb.position
 					_pan_start_offset = _pan_offset
 				MOUSE_BUTTON_WHEEL_UP:
+					var old_zoom := _zoom
 					_zoom = clampf(_zoom + ZOOM_STEP, ZOOM_MIN, ZOOM_MAX)
+					if _zoom != old_zoom:
+						_dirty = true
 				MOUSE_BUTTON_WHEEL_DOWN:
+					var old_zoom := _zoom
 					_zoom = clampf(_zoom - ZOOM_STEP, ZOOM_MIN, ZOOM_MAX)
+					if _zoom != old_zoom:
+						_dirty = true
 		else:
 			if mb.button_index == MOUSE_BUTTON_MIDDLE:
 				_is_panning = false
@@ -476,17 +488,17 @@ func _gui_input(event: InputEvent) -> void:
 		var mm := event as InputEventMouseMotion
 		if _is_panning:
 			_pan_offset = _pan_start_offset + (mm.position - _pan_start)
+			_dirty = true
 		else:
 			_update_hover(mm.position)
 
 
-func _handle_click(pos: Vector2) -> void:
+## Find the system_id of the nearest node to screen position, or "" if none within HIT_RADIUS.
+func _find_nearest_system(pos: Vector2) -> String:
 	var sz: Vector2 = get_rect().size
 	var center: Vector2 = sz * MAP_CENTER_FRACTION + _pan_offset
-
 	var best_dist: float = HIT_RADIUS
 	var best_sid: String = ""
-
 	for node: Dictionary in _nodes:
 		var sid: String = node.get("system_id", "")
 		if not _node_positions.has(sid):
@@ -496,30 +508,22 @@ func _handle_click(pos: Vector2) -> void:
 		if dist < best_dist:
 			best_dist = dist
 			best_sid = sid
+	return best_sid
 
-	if best_sid != "":
-		_selected_system = best_sid
+
+func _handle_click(pos: Vector2) -> void:
+	var nearest := _find_nearest_system(pos)
+	if nearest != "":
+		_selected_system = nearest
 		_show_edges = true
 	else:
 		_selected_system = ""
 		_show_edges = false
+	_dirty = true
 
 
 func _update_hover(pos: Vector2) -> void:
-	var sz: Vector2 = get_rect().size
-	var center: Vector2 = sz * MAP_CENTER_FRACTION + _pan_offset
-
-	var best_dist: float = HIT_RADIUS
-	var best_sid: String = ""
-
-	for node: Dictionary in _nodes:
-		var sid: String = node.get("system_id", "")
-		if not _node_positions.has(sid):
-			continue
-		var node_pos: Vector2 = center + _node_positions[sid] * _zoom
-		var dist: float = pos.distance_to(node_pos)
-		if dist < best_dist:
-			best_dist = dist
-			best_sid = sid
-
-	_hovered_system = best_sid
+	var nearest := _find_nearest_system(pos)
+	if nearest != _hovered_system:
+		_hovered_system = nearest
+		_dirty = true