Add blood decals, gore, mobile HUD, web start gate + touch/perf tests

Remove tools/fstest.html scratch page used to probe browser
fullscreen/orientation APIs.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EznnY8rH2dXhtono1kwsXg

main_menu.gd

@@ -100,6 +100,12 @@ func _ready() -> void:
 	exit_button.pressed.connect(_on_exit_pressed)
 	options_back.pressed.connect(_close_subpanels)
 	credits_back.pressed.connect(_close_subpanels)
+	# The Options panel is keyboard rebinds + desktop-shaped audio rows — meaningless on a
+	# phone, so drop the entry point on touch devices.
+	options_button.visible = not Controls.use_touch_ui()
+	# On the web build get_tree().quit() just freezes the canvas (you can't close a browser
+	# tab from script), so Exit has nowhere to go — hide it. Native desktop keeps it.
+	exit_button.visible = not OS.has_feature("web")
 	_apply_theme()
 	_build_version_label()
 	_build_options_toggles()