Add idempotent object deletion

docs/internal/storage.md

@@ -16,6 +16,7 @@ operator-selected storage fields and credential mechanisms belong in
 - `Download(ctx, key, localPath)`
 - `Upload(ctx, localPath, key, opts)`
 - `UploadConditional(ctx, source, key, opts, condition)`
+- `Delete(ctx, key)` removes one object and succeeds when it is already absent
 - `Exists(ctx, key)`
 
 Key invariant:
@@ -47,6 +48,8 @@ not own discovery, defaults, or configuration validation.
 - `Read` binds a returned body to its S3 ETag. `UploadConditional` maps an ETag
   match or absence precondition directly to the provider request and reports a
   failed precondition without performing a local check-then-write replacement.
+- `Delete` maps one normalized key to the provider delete-object operation and
+  treats an absent object as success.
 - `Exists` maps not-found responses to `false`.
 
 ## Invariants

docs/roadmap/implementation.md

@@ -84,7 +84,7 @@ message. Update documentation alongside observable changes.
 
 ## Stage 1 — Add Idempotent Object Deletion
 
-**Status:** Pending
+**Status:** Completed
 
 ### Goal