Add override prompt variable (#301)

* Add override prompt variable

* create test

* Fix typechecks

* remove use of `any` for additional type-safety

---------

Co-authored-by: km-anthropic <km-anthropic@users.noreply.github.com>

action.yml

@@ -50,6 +50,10 @@ inputs:
     description: "Direct instruction for Claude (bypasses normal trigger detection)"
     required: false
     default: ""
+  override_prompt:
+    description: "Complete replacement of Claude's prompt with custom template (supports variable substitution)"
+    required: false
+    default: ""
   mcp_config:
     description: "Additional MCP configuration (JSON string) that merges with the built-in GitHub MCP servers"
   additional_permissions:
@@ -142,6 +146,7 @@ runs:
         DISALLOWED_TOOLS: ${{ inputs.disallowed_tools }}
         CUSTOM_INSTRUCTIONS: ${{ inputs.custom_instructions }}
         DIRECT_PROMPT: ${{ inputs.direct_prompt }}
+        OVERRIDE_PROMPT: ${{ inputs.override_prompt }}
         MCP_CONFIG: ${{ inputs.mcp_config }}
         OVERRIDE_GITHUB_TOKEN: ${{ inputs.github_token }}
         GITHUB_RUN_ID: ${{ github.run_id }}