Protect initial pipeline stage resume semantics

docs/internal/stage-merge.md

@@ -29,9 +29,23 @@ Normalize raw transcript inputs and merge into base transcript via Seriatim.
 - base transcript must validate before stage success.
 - report output is config-gated.
 
+## Resume Evidence
+
+Merge records a versioned semantic-configuration fingerprint for the Seriatim
+merge operation, output schema, coalesce gap, and every configured advanced
+merge transformation. A change reruns merge and stales only its fixed
+descendants; prepare and transcribe remain reusable. Binary path, timeout,
+report emission, logs, and diagnostic retention are operational exclusions.
+
+Configuration or resources loaded privately inside Seriatim are outside
+Narratio's observable contract and require `--force` when changed. An existing
+successful merge record without evidence reruns once when selected.
+
 ## Related Contracts And Tests
 
 - [Seriatim](../integrations/seriatim.md) owns subprocess and output semantics.
 - [Configuration](../config.md#pipeline) owns operator-selected Seriatim values.
 - Implementation and tests: `internal/stage/merge.go`,
-  `internal/stage/merge_test.go`
+  `internal/stage/merge_test.go`,
+  `internal/stage/semantic_contracts_initial.go`, and
+  `internal/stage/semantic_contracts_initial_test.go`