Protect initial pipeline stage resume semantics

docs/internal/stage-prepare.md

@@ -57,6 +57,21 @@ mapping, while the isolated legacy reader rejects ambiguous fallback matches.
 - managed `previous/` state represents only the current requirement set.
 - `manifest.inputs` ordering is deterministic (`kind`, `path`).
 
+## Resume Evidence
+
+Prepare records a versioned semantic-configuration fingerprint for the
+resolved campaign/session selection, local-versus-S3 audio mode and canonical
+audio names, stable-input ownership/presence, previous-session identity, and
+the effective previous-artifact requirement set. A change reruns prepare and
+stales its fixed descendants. Existing successful records without this
+evidence rerun once when selected.
+
+Workspace, spool, and cache placement and absolute source relocation are not
+semantic when logical selection, canonical names, and bytes are equivalent.
+The fingerprint deliberately does not read or rehash large audio. Prepared
+input checksums remain the content provenance; force prepare after changing
+source bytes that are not otherwise reflected by the semantic selection.
+
 ## Related Contracts And Tests
 
 - [Configuration](../config.md) owns audio selection, stable input fields, and
@@ -66,5 +81,8 @@ mapping, while the isolated legacy reader rejects ambiguous fallback matches.
 - [Storage Internals](storage.md) and [Artifact Internals](artifacts.md) explain
   the internal collaborators.
 - Implementation and tests: `internal/stage/prepare.go`,
-  `internal/stage/prepare_test.go`, `internal/audio/s3_audio_test.go`,
+  `internal/stage/prepare_test.go`,
+  `internal/stage/semantic_contracts_initial.go`,
+  `internal/stage/semantic_contracts_initial_test.go`,
+  `internal/audio/s3_audio_test.go`,
   `internal/previouscache/*_test.go`