Add documentation for prompt, profile, schema, and main configuration files

docs/config/profile-definitions.md

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+# Execution Profile Definitions
+
+Execution Profiles define **how** Scriptorium calls an LLM endpoint.
+
+A profile file is YAML, typically stored under `profiles/`, for example `profiles/local-quality.yaml`.
+
+## Complete Example
+
+```yaml
+id: local-quality
+endpoint: http://localhost:8000/v1
+model: gpt-4.1
+temperature: 0.0
+max_tokens: 1200
+top_p: 1.0
+timeout_seconds: 180
+reasoning_effort: medium
+api_key_env: SCRIPTORIUM_API_KEY
+extra_params:
+  provider: openrouter
+  route: fallback
+```
+
+## Available Options
+
+- `id` (required): Unique profile identifier used by `--profile` or prompt `default_profile`.
+- `endpoint` (required): OpenAI-compatible base URL, usually ending in `/v1`.
+- `model` (required): Model name to request at that endpoint.
+- `temperature` (optional): Sampling temperature. Valid range is `0` to `2`.
+- `max_tokens` (optional): Max completion tokens. Must be `>= 0`.
+- `top_p` (optional): Nucleus sampling parameter. Valid range is `0` to `1`.
+- `timeout_seconds` (optional): Request timeout in seconds. Must be `>= 0`.
+- `reasoning_effort` (optional): Provider/model-specific reasoning level string.
+- `api_key_env` (optional): Environment variable name that holds the API key.
+- `extra_params` (optional): String key/value map for provider-specific parameters.
+
+## Notes and Rules
+
+- Raw API keys are not supported. Do **not** add `api_key` fields.
+- Unknown YAML fields fail to load (strict decoding).
+- If `api_key_env` is set, the environment variable must be present when the run executes.