`spacelift.plan.json` is not actually created and therefore `get_plan_json` doesn't work

[dylanratcliffe]

Bug Report: get_plan_json fails because spacelift.plan.json is missing in Spacelift runner environment

Summary

The SpaceforgePlugin.get_plan_json() helper method consistently fails in a standard Spacelift runner environment because the expected file spacelift.plan.json does not exist. The runner only provides the binary plan file (spacelift.plan).

Expected Behavior

Calling self.get_plan_json() should automatically return the parsed JSON content of the current Terraform/OpenTofu plan, either by reading a pre-existing JSON file or converting the binary plan on demand.

Actual Behavior

The method returns None and logs an error: spacelift.plan.json does not exist.

Evidence

1. File Listing: Debugging output from the plugin execution in a Spacelift runner shows the file spacelift.plan exists in the workspace root, but spacelift.plan.json is absent.

   (Overmind) Files in /mnt/workspace/source: ..., .terraform, spacelift.plan
   (Overmind) spacelift.plan.json does not exist.
   

2. Framework Code: The implementation of get_plan_json in spaceforge/plugin.py simply attempts to read spacelift.plan.json without any fallback logic to convert the binary plan.

   def get_plan_json(self) -> Optional[Dict[str, Any]]:
       plan_json = f"{self._workspace_root}/spacelift.plan.json"
       if not os.path.exists(plan_json):
           self.logger.error("spacelift.plan.json does not exist.")
           return None
       # ...

3. Test Gap: The unit test test_should_return_plan_data_when_plan_file_exists passes because it manually writes a JSON file to the test directory, masking the fact that the real environment doesn't provide it.
4. Workaround Required: To make the plugin work, we had to manually implement a fallback in the plugin code that detects the available IAC tool (terraform or tofu) and runs show -json spacelift.plan.

Impact

Any plugin developers relying on get_plan_json() as documented will find it broken in production unless Spacelift is specifically configured to generate that JSON artifact (which is not the default).

Suggested Fix

Update SpaceforgePlugin.get_plan_json() to:

1. Check for spacelift.plan.json first.
2. If missing, check for spacelift.plan.
3. If binary plan exists, convert it using terraform show -json (or tofu) and return the parsed result.