Complete cleanup sweep and align internal artifact docs

docs/internal/artifacts.md

@@ -76,6 +76,12 @@ Trim invariants:
 - retained order follows input transcript order.
 - output IDs are reassigned to `1..N`.
 
+Run layer (`run.go`):
+
+- executes end-to-end trim orchestration from validated config
+- writes output JSON
+- optionally writes report JSON with `trim-audit`
+
 ## Normalize internals
 
 `internal/normalize` canonicalizes transcript-like JSON input into a selected