Add regeneration instructions to README

Co-authored-by: Jay Hack <jay@codegen.com>

Author: codegen-sh[bot]

README.md

@@ -1,6 +1,60 @@
 # codegen-api-client
 API for application developers
 
+## Regenerating the Client
+
+This client is automatically generated from the OpenAPI specification. To regenerate the client:
+
+### Using Docker (Recommended)
+
+```bash
+# Pull the OpenAPI Generator Docker image (version 7.12.0 to match current)
+docker pull openapitools/openapi-generator-cli:v7.12.0
+
+# Run the generator (from the repository root)
+docker run --rm -v "${PWD}:/local" openapitools/openapi-generator-cli:v7.12.0 generate \
+  -i /local/gen/openapi.yaml \
+  -g python \
+  -c /local/gen/config.json \
+  -o /local
+```
+
+### Alternative: Using NPM
+
+```bash
+# Install via npm
+npm install -g @openapitools/openapi-generator-cli@7.12.0
+
+# Set the version
+npx @openapitools/openapi-generator-cli version-manager set 7.12.0
+
+# Generate the client
+npx @openapitools/openapi-generator-cli generate \
+  -i ./gen/openapi.yaml \
+  -g python \
+  -c ./gen/config.json \
+  -o .
+```
+
+### After Generation
+
+```bash
+# Build the package
+uv build
+
+# Optionally publish the package
+uv publish
+```
+
+### Important Notes
+
+- The OpenAPI spec at `./gen/openapi.yaml` is the source of truth for this client
+- Update this spec file first if you need to update the API client
+- The configuration in `./gen/config.json` specifies the package name as "codegen_api_client"
+- GitHub workflows handle testing and publishing, but not regeneration
+
+---
+
 This Python package is automatically generated by the [OpenAPI Generator](https://openapi-generator.tech) project:
 
 - API version: 1.0.0
@@ -114,6 +168,3 @@ Endpoints do not require authorization.
 
 ## Author
 
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