Shore should setup a validated API contract between the CLI and Renderer

Currently missing parameters are not easily testable.
During manifestation of JSonnet, params are read from Render.yaml and passed to the render.

Missing parameters aren't debuggable due to the amount of abstraction introduced by Shore.

The error produced when running with an empty empty `render.yml` file:
```
ERRO[0000] Renderer.Render returned an error RUNTIME ERROR: Field does not exist: application
/Users/liberms/code/platform/testshore/main.pipeline.jsonnet:5:20-38 object
During manifestation
RUNTIME ERROR: Field does not exist: application
/Users/liberms/code/platform/testshore/main.pipeline.jsonnet:5:20-38 object
During manifestation
```

Start by tracing how the CLI reads parameters from Render.yaml or an empty render.yml and passes them to Renderer.Render during manifestation. Review the current error path and the boundary between the CLI and Renderer. Done means missing parameters are validated at that boundary and produce an actionable, testable error instead of the Jsonnet field-missing message.

Written by the indexing model from the issue text.