Bind audio cache reuse to remote identity

docs/internal/command-restore.md

@@ -69,7 +69,9 @@ Audio restore path:
 
 - uses `audio.MaterializeS3Audio`;
 - integrates spool and S3 audio cache paths;
-- supports cache-hit reuse without object redownload.
+- reuses cached audio only when its no-follow regular file, content digest, and
+  identity sidecar all match the selected remote object version; otherwise it
+  refreshes through the durable download path.
 
 ## Reporting Contract
 

docs/operations.md

@@ -329,6 +329,10 @@ Cache layout (durable S3 audio cache):
 
 - `{cache.root}/s3/{bucket}/...`
 
+Each cached audio file has an adjacent managed identity record. It binds the
+file to its remote object version and verified digest; deleting or altering the
+record simply causes Narratio to download and verify the object again.
+
 ### Workspace Permissions
 
 Ordinary Narratio workspace content is intentionally shareable with the

docs/policy/architecture.md

@@ -157,6 +157,10 @@ Canonical helpers own workspace, spool, cache, session, run, input, transcript,
 artifact, log, report, configuration, and publish-current paths. Callers must
 not reconstruct canonical paths through scattered string concatenation.
 
+Reusable audio cache entries require a typed record that binds a confined,
+no-follow regular file and its digest to the selected remote object identity.
+Size alone and unqualified multipart ETags are not content-integrity evidence.
+
 Artifact resolution is deterministic and manifest-aware. Producers materialize
 canonical outputs before reporting success, and consumers resolve declared
 artifact identities rather than infer files from unrelated directory contents.

docs/roadmap/implementation.md

@@ -34,7 +34,7 @@ All stages are pending when this plan is created.
 | 16 | Persist retryable post-commit cleanup state | COR-006, COR-007 | Completed |
 | 17 | Bind restore/status to a committed snapshot and reject conflicts | COR-008, COR-009, TST-005 | Completed |
 | 18 | Serialize restore transitions and make restored paths portable | RSK-006, RSK-008 | Completed |
-| 19 | Bind audio cache reuse to remote object identity | RSK-007 | Pending |
+| 19 | Bind audio cache reuse to remote object identity | RSK-007 | Completed |
 | 20 | Unify previous-source readiness and eliminate duplicate transfers | COR-010, EFF-001 | Pending |
 | 21 | Tighten configuration parsing, values, and expectations | COR-012–COR-015, TST-011, TST-014 | Pending |
 | 22 | Make product configuration truthful and own remote temp files | COR-024, RSK-009, ARC-004 | Pending |