fix(admin): always send dry_run on storage-GC requests

`run_storage_gc` built its body with `dry_run.then_some(true)`. The
generated SDK field is `Option<bool>` carrying
`#[serde(skip_serializing_if = "Option::is_none")]`, so on a live run
(no `--dry-run`) the `None` dropped the key entirely and the CLI posted
`{}` to `POST /api/v1/admin/storage-gc`.

That relied on the server defaulting the field. artifact-keeper#3619
removes that default: `dry_run` becomes required and unknown fields are
rejected, so `{}` is refused with 422 and no GC runs. `ak admin
storage-gc run --dry-run` was always fine — it sent `{"dry_run": true}`.

Send the value unconditionally instead, via a small `storage_gc_body`
helper so the body is testable without a client. A live run now posts
`{"dry_run": false}`, which is what the 1.8.x backend already means by
an empty body, so this is safe to merge before #3619 and required
after it.

The added test asserts both bodies; restoring `then_some(true)` fails
it with `left: Object {}`.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01W6pg381RiaM9GsdVEyrN8M

Author: brandonrc

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- `ak admin storage-gc run` now always sends `dry_run` explicitly, so a live run posts `{"dry_run": false}` instead of an empty body. Companion to artifact-keeper#3619, which makes `dry_run` required on the storage-GC endpoint and rejects unknown fields (422)
+
 ## [1.2.0] - 2026-07-13
 
 ### Added

src/commands/admin.rs

@@ -3975,13 +3975,23 @@ async fn toggle_ci_oidc_mapping(
 
 // ---- Storage GC and reports ----
 
+/// Build the `POST /api/v1/admin/storage-gc` request body.
+///
+/// `dry_run` is always sent explicitly. The generated field is
+/// `Option<bool>` with `skip_serializing_if = "Option::is_none"`, so a `None`
+/// drops the key and posts `{}` — which the backend rejects with 422 once
+/// artifact-keeper#3619 lands (`dry_run` required, unknown fields denied).
+fn storage_gc_body(dry_run: bool) -> artifact_keeper_sdk::types::StorageGcRequest {
+    artifact_keeper_sdk::types::StorageGcRequest {
+        dry_run: Some(dry_run),
+    }
+}
+
 async fn run_storage_gc(dry_run: bool, global: &GlobalArgs) -> Result<()> {
     let client = client_for(global)?;
     let spinner = output::spinner("Running storage garbage collection...");
 
-    let body = artifact_keeper_sdk::types::StorageGcRequest {
-        dry_run: dry_run.then_some(true),
-    };
+    let body = storage_gc_body(dry_run);
 
     let r = client
         .run_storage_gc()
@@ -7204,6 +7214,21 @@ mod tests {
         }
     }
 
+    #[test]
+    fn storage_gc_body_always_sends_dry_run() {
+        // A live run must send `"dry_run": false`, not an empty body: the
+        // backend requires the field and rejects unknown ones
+        // (artifact-keeper#3619).
+        assert_eq!(
+            serde_json::to_value(storage_gc_body(false)).unwrap(),
+            json!({ "dry_run": false })
+        );
+        assert_eq!(
+            serde_json::to_value(storage_gc_body(true)).unwrap(),
+            json!({ "dry_run": true })
+        );
+    }
+
     #[test]
     fn parse_storage_gc_oci_report() {
         let cli = parse(&["test", "storage-gc", "oci-report", "--grace-hours", "48"]);