Complete pre-1.0 release hardening

docs/configuration.md

@@ -99,6 +99,9 @@ diagnostics:
   retention: auto
 ```
 
+`context.description` provides background-only transcript context for prompts.
+If both config and CLI provide a description, `--transcript-description` takes precedence.
+
 `output.schema` supports the built-in output schema registry values:
 - `bare-segments` (default)
 - `audita-v1`