feat: Add fast startup fetch and background caching

- Add  for quick startup using first N feeds
- Add background thread for full fetch and caching
- Update  to use fast fetch
- Update docs and skills

tests/test_pipeline_e2e.py

@@ -218,9 +218,10 @@ class TestPipelineE2EHappyPath:
 
         assert result.success
         frame = display.frames.get(timeout=1)
-        assert "Line A" in frame
-        assert "Line B" in frame
-        assert "Line C" in frame
+        # Camera stage pads lines to viewport width, so check for substring match
+        assert any("Line A" in line for line in frame)
+        assert any("Line B" in line for line in frame)
+        assert any("Line C" in line for line in frame)
 
     def test_empty_source_produces_empty_buffer(self):
         """An empty source should produce an empty (or blank) frame."""
@@ -263,7 +264,10 @@ class TestPipelineE2EEffects:
 
         assert result.success
         frame = display.frames.get(timeout=1)
-        assert "[FX1]" in frame, f"Marker not found in frame: {frame}"
+        # Camera stage pads lines to viewport width, so check for substring match
+        assert any("[FX1]" in line for line in frame), (
+            f"Marker not found in frame: {frame}"
+        )
         assert "Original" in "\n".join(frame)
 
     def test_effect_chain_ordering(self):
@@ -387,7 +391,7 @@ class TestPipelineE2EStageOrder:
         # All regular (non-overlay) stages should have metrics
         assert "source" in stage_names
         assert "render" in stage_names
-        assert "display" in stage_names
+        assert "queue" in stage_names  # Display stage is named "queue" in the test
         assert "effect_m" in stage_names