feat: initialize standalone image-filter

Rename the distribution to image-filter and imports to image_filter.
Keep medical fixtures local and document their setup for fresh clones.
Include composite pipelines, consistent examples, and class diagrams.

docs/components.mmd

@@ -0,0 +1,41 @@
+classDiagram
+direction TB
+class ImageFilter {
+  <<abstract>>
+  +Capabilities capabilities
+  +apply(image, metadata) FilterResult
+  +apply_batch(items) list~FilterResult~
+}
+class NumericFilter {
+  <<abstract>>
+  +apply(image, metadata) FilterResult
+  #_apply_with_layout(image, metadata, layout) FilterResult
+  #_compute(image, layout) ndarray
+  #_history_entry(image, output, layout) dict
+}
+class Pipeline {
+  +tuple~ImageFilter~ steps
+  +Capabilities capabilities
+  +apply(image, metadata) FilterResult
+}
+class SliceWise {
+  +ImageFilter filter
+  +int axis
+  +apply(image, metadata) FilterResult
+  #_compute(image, layout) ndarray
+}
+ImageFilter <|-- NumericFilter
+ImageFilter <|-- Pipeline
+NumericFilter <|-- SliceWise
+Pipeline "0..*" o-- "1..*" ImageFilter : ordered children
+SliceWise "0..*" o-- "1" ImageFilter : adapts
+NumericFilter <|-- MeanFilter
+NumericFilter <|-- GaussianFilter
+NumericFilter <|-- MedianFilter
+NumericFilter <|-- SobelFilter
+NumericFilter <|-- LaplacianFilter
+NumericFilter <|-- LoGFilter
+NumericFilter <|-- LawsFilter
+NumericFilter <|-- GaborFilter
+NumericFilter <|-- CannyFilter
+NumericFilter <|-- WaveletFilter