Require manifest-backed local artifacts

docs/troubleshooting.md

@@ -428,6 +428,25 @@ narratio analyze 2026-04-04 --artifacts session_recap
 Relevant references: [Operations: Artifact Selection](./operations.md#artifact-selection)
 and [Artifact Internals](./internal/artifacts.md#resolution-rules).
 
+## Built-in transcript or bounds source is unavailable
+
+Symptom:
+
+- analyze, extract, render, or publish says a built-in source is unavailable
+  even though a file exists at its usual session path.
+
+Likely cause:
+
+- the producing stage has not succeeded, its output lacks the exact registered
+  source, run ID, or checksum, its evidence is duplicated or stale, or the
+  durable bytes no longer match the manifest checksum.
+
+Safe fix:
+
+- do not copy or rename the file to make it discoverable. Rerun the producing
+  stage to regenerate both the bytes and current manifest evidence, then retry
+  the consumer.
+
 ## Legacy aggregate analysis requires regeneration
 
 Symptom: