Support multiple IDs in assign and unassign

.surface-breaking

@@ -1,7 +1,9 @@
 ARG basecamp assign 00 <todo_id>
+ARG basecamp assign 00 <id>
+ARG basecamp unassign 00 <todo_id>
+ARG basecamp unassign 00 <id>
 ARG basecamp url 00 [parse]
 ARG basecamp url 01 <url>
-ARG basecamp unassign 00 <todo_id>
 ARG basecamp upload archive 00 <id|url>
 ARG basecamp upload doc create 00 <title>
 ARG basecamp upload doc create 01 [content]

e2e/smoke/smoke_assign.bats

@@ -37,3 +37,40 @@ setup_file() {
   assert_success
   assert_json_value '.ok' 'true'
 }
+
+@test "assign handles multiple todos in one command" {
+  # Create two fresh todos
+  local todo1_out todo2_out
+  todo1_out=$(basecamp todo "Batch assign 1 $(date +%s)" --list "$QA_TODOLIST" -p "$QA_PROJECT" --json 2>/dev/null) || {
+    mark_unverifiable "Cannot create todo 1 for batch assign test"
+    return
+  }
+  todo2_out=$(basecamp todo "Batch assign 2 $(date +%s)" --list "$QA_TODOLIST" -p "$QA_PROJECT" --json 2>/dev/null) || {
+    mark_unverifiable "Cannot create todo 2 for batch assign test"
+    return
+  }
+  local id1 id2
+  id1=$(echo "$todo1_out" | jq -r '.data.id // empty')
+  id2=$(echo "$todo2_out" | jq -r '.data.id // empty')
+  [[ -n "$id1" && -n "$id2" ]] || mark_unverifiable "No todo IDs returned"
+
+  echo "$id1" > "$BATS_FILE_TMPDIR/batch_assign_id1"
+  echo "$id2" > "$BATS_FILE_TMPDIR/batch_assign_id2"
+
+  run_smoke basecamp assign "$id1" "$id2" --to me -p "$QA_PROJECT" --json
+  assert_success
+  assert_json_value '.ok' 'true'
+}
+
+@test "unassign handles multiple todos in one command" {
+  local id1_file="$BATS_FILE_TMPDIR/batch_assign_id1"
+  local id2_file="$BATS_FILE_TMPDIR/batch_assign_id2"
+  [[ -f "$id1_file" && -f "$id2_file" ]] || mark_unverifiable "No todos created in prior test"
+  local id1 id2
+  id1=$(<"$id1_file")
+  id2=$(<"$id2_file")
+
+  run_smoke basecamp unassign "$id1" "$id2" --from me -p "$QA_PROJECT" --json
+  assert_success
+  assert_json_value '.ok' 'true'
+}