Add README.md file for the factory subdirectory

experimental/builder/include/ck_tile/builder/factory/README.md

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+# Convolution Factory Directory
+
+This directory implements compile-time dispatch from high-level signature algorithm descriptors to our exisitng specialized convolution kernel implementations.
+
+## Design Overview
+
+The factory system operates in two phases:
+
+1. **Algorithm Classification**: The function `make_conv_instance` in  `conv_dispatcher.hpp` inspects the signature and algorithm descriptors to determine which kernel variant they satisfy (XDL V3, XDL, WMMA, DL, or Large Tensor)
+
+2. **Factory Instantiation**: Each factory (`conv_fwd_*_factory.hpp`) transforms builder descriptors into CK device operation template parameters and instantiates the corresponding kernel device operation.
+
+## Key Files
+
+- **`conv_dispatcher.hpp`**: Entry point with `make_conv_instance()` function. Contains dispatch logic and algorithm classification predicates. **Start here** to understand the overall flow.
+
+- **`conv_fwd_*_factory.hpp`**: Individual factories for each kernel variant. Each extracts configuration from descriptors, validates parameters, and instantiates the underlying CK device operation.
+
+- **`helpers/`**: Transformation utilities that map builder types to CK device operation parameters (layouts, data types, elementwise ops, block configurations, etc.)
+
+## Usage
+
+```cpp
+#include "ck_tile/builder/factory/conv_dispatcher.hpp"
+
+using Factory = decltype(make_conv_instance<signature, algorithm, "v1">());
+```
+
+The dispatcher automatically selects the appropriate factory following explicit logic.