Add render export adapter contract

examples/render/fake-render-request.yaml

@@ -0,0 +1,16 @@
+schema_version: markitect.render.export.v1
+operation: render-artifact
+profile: docs
+source_path: examples/render/source.md
+source: |
+  # Fake Render Example
+
+  This fixture exercises the render/export adapter contract without invoking a
+  real renderer.
+options:
+  deterministic: true
+policy:
+  external_process: false
+  filesystem_write: false
+metadata:
+  purpose: render-contract-fixture