Initial commit: SpaceshipTest, a top-down space RTS in Godot 4.7.1

A fleet of neon-outlined ships explores a procedurally generated, seeded
infinite world: tap/joystick steering, pinch zoom, formation pivoting,
planet landings, an ore economy with extractors and haulers, and player
built structures (mothership, ship crafter, command centre).

All art is hand-drawn with draw_* calls rather than textures, and the
backgrounds are camera-relative shaders so they stay precise at large
world coordinates.

Includes a 35-test headless suite (tests/run_tests.sh) plus screenshot
tooling that renders real frames through Xvfb and Mesa softpipe, since
--headless has no GPU.

Excluded from version control: .godot/ (import cache, and it holds
export credentials), builds/, android/build/ and packaged APKs - all
regenerable, and ~325 MB combined.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tests/_screenshot_tool.gd

@@ -0,0 +1,53 @@
+extends SceneTree
+
+# Reusable screenshot tool - NOT run via run_tests.sh (underscore prefix).
+# Loads a given scene, waits for a given number of frames to render, then
+# saves a PNG and quits. Must be run WITHOUT --headless (that forces
+# Godot's dummy/null renderer) - see tests/screenshot.sh for the full
+# invocation (Xvfb + Mesa softpipe; llvmpipe's JIT crashes with SIGILL in
+# this environment, softpipe's non-JIT rasterizer does not).
+#
+# Args (after `--`): <scene_res_path> <output_png_path> [wait_frames]
+
+var wait_frames: int = 60
+var frames: int = 0
+var scene_path: String
+var output_path: String
+var loaded_scene: Node
+
+
+func _initialize() -> void:
+	var args: PackedStringArray = OS.get_cmdline_user_args()
+	if args.size() < 2:
+		printerr("usage: -- <scene_res_path> <output_png_path> [wait_frames]")
+		quit(1)
+		return
+
+	scene_path = args[0]
+	output_path = args[1]
+	if args.size() >= 3:
+		wait_frames = int(args[2])
+
+	var packed: PackedScene = load(scene_path)
+	if packed == null:
+		printerr("could not load scene: %s" % scene_path)
+		quit(1)
+		return
+
+	loaded_scene = packed.instantiate()
+	root.add_child(loaded_scene)
+
+
+func _process(_delta: float) -> bool:
+	frames += 1
+	if frames < wait_frames:
+		return false
+	var img: Image = root.get_viewport().get_texture().get_image()
+	var err: int = img.save_png(output_path)
+	if err != OK:
+		printerr("save_png failed with error %d" % err)
+		quit(1)
+		return true
+	print("SCREENSHOT_SAVED: %s (%s)" % [output_path, str(img.get_size())])
+	quit(0)
+	return true