Add trim configuration contract

README.md

@@ -32,6 +32,40 @@ Narratio expects two YAML files:
 
 YAML decoding is strict (`KnownFields(true)`), so unknown fields fail fast.
 
+## Trim Configuration (Scaffold)
+
+`pipeline.trim` is optional. If omitted, no trim config is loaded. If `trim.enabled` is omitted, it defaults to `false`.
+
+When `trim.enabled: true`:
+
+- `trim.output_path` is required
+- `trim.bounds.prompt_id` is required
+- `trim.bounds.transcript_input_name` is required
+- `trim.bounds.output_path` is required
+- `trim.bounds.timeout` must be a valid Go duration when provided
+- `trim.bounds.render_debug: true` requires `trim.bounds.render_output_path`
+- `trim.bounds.profile_id` may be empty to use the prompt default profile
+
+Trim paths are treated as session-workdir-relative when not absolute.
+
+Example trim scaffold config:
+
+```yaml
+trim:
+  enabled: true
+  output_path: "transcripts/trimmed.json"
+  bounds:
+    prompt_id: "dnd_session.bounds"
+    profile_id: ""
+    transcript_input_name: "transcript"
+    output_path: "artifacts/session_bounds.json"
+    timeout: "10m"
+    render_debug: false
+    render_output_path: "artifacts/session_bounds.render.json"
+  seriatim:
+    report: false
+```
+
 ## Scriptorium Configuration
 
 `pipeline.scriptorium` is optional. When present, Narratio validates and uses it for analyze-stage artifact generation.