fix(#2488): verify assignee change landed instead of trusting forge 200

hive-forge/src/verbs/assign.rs

@@ -60,6 +60,32 @@ pub fn run(client: &Client, args: Args) -> Result<()> {
         .iter()
         .filter_map(|u| u.login.as_deref())
         .collect();
+    // Verify the mutation actually landed. Forgejo silently drops an assignee
+    // change the caller isn't permitted to make (e.g. unassigning another
+    // user) and echoes back the *unchanged* list with a 200 — so trusting the
+    // success status reports a no-op as success. Diff the returned list
+    // against the intent and fail loudly instead.
+    let still_present = logins.iter().any(|&u| u == args.user);
+    if args.remove && still_present {
+        anyhow::bail!(
+            "assignee '{}' is still assigned to #{} after remove — the forge \
+             rejected the change (likely insufficient permission to unassign \
+             this user). current assignees: [{}]",
+            args.user,
+            args.number,
+            logins.join(", ")
+        );
+    }
+    if !args.remove && !still_present {
+        anyhow::bail!(
+            "assignee '{}' is not assigned to #{} after add — the forge rejected \
+             the change (the user may not exist or lack access to this repo). \
+             current assignees: [{}]",
+            args.user,
+            args.number,
+            logins.join(", ")
+        );
+    }
     print_json(&json!({
         "number": resp.number,
         "assignees": logins,