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/architecture.md

@@ -0,0 +1,123 @@
+# Image Filter class diagrams
+
+These UML-style Mermaid diagrams describe the implemented classes in
+`src/image_filter`. Open this Markdown in a Mermaid-capable viewer, or use
+the adjacent `.mmd` source files with Mermaid CLI.
+
+## Composite and numerical filters
+
+```mermaid
+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
+```
+
+ImageFilter is the public Component, Pipeline the Composite, and the ten
+concrete numerical filters the Leaves. NumericFilter shares validation and
+history behavior; it is an internal abstract implementation, not a separate
+public filtering operation. SliceWise is an adapter that can wrap a Leaf or
+a Pipeline.
+
+The hollow diamond denotes aggregation: immutable children can be shared
+between pipelines and remain valid independently of any parent. A Pipeline
+contains at least one child and executes children in order. Inheritance arrows
+point toward the base class. Public methods use +; internal methods use #.
+
+## Input, output, and capability model
+
+```mermaid
+classDiagram
+direction LR
+class ImageItem {
+  +ndarray image
+  +Mapping metadata
+}
+class FilterResult {
+  +ndarray image
+  +Mapping metadata
+}
+class SpatialLayout {
+  +int dimension
+  +tuple spatial_axes
+  +tuple singleton_axes
+  +int channel_axis
+}
+class Capabilities {
+  +frozenset spatial_dimensions
+  +str accepted_dtypes
+  +str input_range
+  +str output_dtype
+  +bool preserves_shape
+  +bool supports_channels
+}
+class ImageFilter {
+  <<abstract>>
+  +apply(image, metadata) FilterResult
+  +apply_batch(items) list~FilterResult~
+}
+class NumericFilter {
+  <<abstract>>
+}
+ImageFilter <|-- NumericFilter
+ImageFilter ..> ImageItem : consumes in batches
+ImageFilter ..> FilterResult : returns
+ImageFilter ..> Capabilities : declares
+NumericFilter ..> SpatialLayout : validates and computes
+```
+
+ImageItem groups an array with metadata for batch execution. FilterResult
+contains the resulting array and copied metadata. SpatialLayout describes the
+effective spatial axes, ignoring singleton axes and excluding an explicitly
+declared channel axis. Capabilities describes supported input dimensions and
+other contracts. Pipeline derives its capabilities from its children.
+
+## Source and presentation order
+
+1. `src/image_filter/base.py`: Component and common numerical behavior.
+2. `src/image_filter/filters.py`: the ten Leaves.
+3. `src/image_filter/pipeline.py`: Composite and slice adapter.
+4. `src/image_filter/model.py`: domain objects and dimension inference.
+5. `examples/01_single_filter.py` through `05_slicewise_pipeline.py`:
+   a shared runner with different component configurations.
+
+Editable sources: [components.mmd](components.mmd) and
+[domain-model.mmd](domain-model.mmd). Keep their diagrams identical to the
+embedded blocks here when changing class relationships.