Refactor: load execution profiles from YAML and split prompt definitions into promptdef repository

internal/promptdef/testdata/valid.yaml

@@ -0,0 +1,19 @@
+id: test-profile
+version: "1.0.0"
+default_profile: test-exec
+description: A valid test prompt definition
+inputs:
+  - name: transcript
+    required: true
+    content_type: text/markdown
+  - name: glossary
+    required: false
+    content_type: text/yaml
+templates:
+  - role: system
+    content: "You are a helpful assistant."
+  - role: user
+    content: 'Analyze this: {{input "transcript"}}'
+output_format: markdown
+validation:
+  validation_mode: basic