feat: rename anthropic_model input to model with backward compatibility

- Add new 'model' input parameter as the preferred way to specify the model
- Keep 'anthropic_model' for backward compatibility with deprecation notice
- Use expression syntax to prioritize 'model' over 'anthropic_model'
- Update README documentation to reflect the change

This allows existing workflows to continue working while encouraging migration to the cleaner 'model' parameter name.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

action.yml

@@ -14,9 +14,12 @@ inputs:
     required: false
 
   # Claude Code configuration
-  anthropic_model:
+  model:
     description: "Model to use (provider-specific format required for Bedrock/Vertex)"
     required: false
+  anthropic_model:
+    description: "DEPRECATED: Use 'model' instead. Model to use (provider-specific format required for Bedrock/Vertex)"
+    required: false
     default: "claude-3-7-sonnet-20250219"
   allowed_tools:
     description: "Additional tools for Claude to use (the base GitHub tools will always be included)"
@@ -98,14 +101,14 @@ runs:
         allowed_tools: ${{ env.ALLOWED_TOOLS }}
         disallowed_tools: ${{ env.DISALLOWED_TOOLS }}
         timeout_minutes: ${{ inputs.timeout_minutes }}
-        anthropic_model: ${{ inputs.anthropic_model }}
+        anthropic_model: ${{ inputs.model || inputs.anthropic_model }}
         mcp_config: ${{ steps.prepare.outputs.mcp_config }}
         use_bedrock: ${{ inputs.use_bedrock }}
         use_vertex: ${{ inputs.use_vertex }}
         anthropic_api_key: ${{ inputs.anthropic_api_key }}
       env:
         # Model configuration
-        ANTHROPIC_MODEL: ${{ inputs.anthropic_model }}
+        ANTHROPIC_MODEL: ${{ inputs.model || inputs.anthropic_model }}
         GITHUB_TOKEN: ${{ steps.prepare.outputs.GITHUB_TOKEN }}
 
         # AWS configuration