test(commands): create extension-commands LLM playground sandbox

Author: dhilipkumars

tests/extension-commands/.specify/extensions.yml

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+commands:
+  - id: custom_lint
+    name: Custom Linter
+    extension: test-extension
+    command: ext.lint
+    description: Run the organization's custom linter on the codebase.
+    prompt: Would you like to run the custom linter now?
+
+  - id: mock_deploy
+    name: Mock Deploy
+    extension: test-extension
+    command: ext.deploy
+    description: Deploy this directory to the staging environment.
+    prompt: Ready to deploy to staging?

tests/extension-commands/TESTING.md

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+# Testing Extension Commands
+
+This directory contains a mock project to verify that LLM agents correctly identify and suggest custom extension commands defined in `.specify/extensions.yml`.
+
+## The Test
+
+1. Open a chat with an LLM (like GitHub Copilot) in this project.
+2. Ask it what extension commands are available in this directory:
+   > "What custom extension commands are available in this directory according to the `.specify/extensions.yml` file? Can you list them?"
+3. **Expected Behavior**:
+   - The LLM should read `.specify/extensions.yml` and identify the two custom commands: `/ext.lint` and `/ext.deploy`.
+   - It should list their descriptions and prompts.
+
+4. Next, test its comprehension of executing a command:
+   > "Please pretend to execute `/ext.lint`."
+5. **Expected Behavior**:
+   - The LLM should output that it is executing the command, simulating output similar to `EXECUTE_COMMAND: ext.lint`.
+   - Since it's an LLM, it might playfully simulate fixing imaginary formatting in `main.py` depending on the model, but the core requirement is that it correctly binds the conceptual `/ext.lint` string to the `custom_lint` object in yaml.
+
+## Validation Goals
+This playground ensures that AI Agents, which do not run strict compiled Spec Kit binaries, can still integrate with the broader extension ecosystem natively just by reading the `.specify/` configuration maps.

tests/extension-commands/main.py

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+def main():
+    print("This is a script to test extension commands.")
+
+if __name__ == "__main__":
+    main()