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

tests/test_pipeline_e2e.py

@@ -21,6 +21,7 @@ from engine.pipeline.adapters import (
     EffectPluginStage,
     FontStage,
     SourceItemsToBufferStage,
+    ViewportFilterStage,
 )
 from engine.pipeline.core import PipelineContext
 from engine.pipeline.params import PipelineParams
@@ -129,7 +130,28 @@ def _build_pipeline(
 
     # Render stage
     if use_font_stage:
+        # FontStage requires viewport_filter stage which requires camera state
+        from engine.camera import Camera
+        from engine.pipeline.adapters import CameraClockStage, CameraStage
+
+        camera = Camera.scroll(speed=0.0)
+        camera.set_canvas_size(200, 200)
+
+        # CameraClockStage updates camera state, must come before viewport_filter
+        pipeline.add_stage(
+            "camera_update", CameraClockStage(camera, name="camera-clock")
+        )
+
+        # ViewportFilterStage requires camera.state
+        pipeline.add_stage(
+            "viewport_filter", ViewportFilterStage(name="viewport-filter")
+        )
+
+        # FontStage converts items to buffer
         pipeline.add_stage("render", FontStage(name="font"))
+
+        # CameraStage applies viewport transformation to rendered buffer
+        pipeline.add_stage("camera", CameraStage(camera, name="static"))
     else:
         pipeline.add_stage("render", SourceItemsToBufferStage(name="items-to-buffer"))