feat: Complete pipeline hot-rebuild implementation with acceptance tests

- Implements pipeline hot-rebuild with state preservation (issue #43)
- Adds auto-injection of MVP stages for missing capabilities
- Adds radial camera mode for polar coordinate scanning
- Adds afterimage and motionblur effects using framebuffer history
- Adds comprehensive acceptance tests for camera modes and pipeline rebuild
- Updates presets.toml with new effect configurations

Related to: #35 (Pipeline Mutation API epic)
Closes: #43, #44, #45

engine/display/__init__.py

@@ -20,6 +20,7 @@ except ImportError:
 from engine.display.backends.multi import MultiDisplay
 from engine.display.backends.null import NullDisplay
 from engine.display.backends.pygame import PygameDisplay
+from engine.display.backends.replay import ReplayDisplay
 from engine.display.backends.terminal import TerminalDisplay
 from engine.display.backends.websocket import WebSocketDisplay
 
@@ -90,6 +91,7 @@ class DisplayRegistry:
             return
         cls.register("terminal", TerminalDisplay)
         cls.register("null", NullDisplay)
+        cls.register("replay", ReplayDisplay)
         cls.register("websocket", WebSocketDisplay)
         cls.register("pygame", PygameDisplay)
         if _MODERNGL_AVAILABLE:
@@ -278,6 +280,7 @@ __all__ = [
     "BorderMode",
     "TerminalDisplay",
     "NullDisplay",
+    "ReplayDisplay",
     "WebSocketDisplay",
     "MultiDisplay",
     "PygameDisplay",