fix(commands): /kick and /ban failures are no longer silent (#216)

rateLimitedActions now collects non-429 failures (and a 429 that exhausted its
retries) and returns them instead of swallowing them; existing callers ignore
the return. /kick and /ban turn the list into a CommandError whose message
names who and why, using the server's own sentence (MatrixError.data.error),
never the URL-bearing toString(); RoomInput's toast shows it verbatim.

Verified headless as a non-moderator: '/kick @alice' → "Could not kick
@alice:localhost: You cannot kick user @alice:localhost."; '/ban @nobody
@alice' → "Could not ban @nobody:localhost, @alice:localhost: You don't have
permission to ban".

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

src/app/features/room/RoomInput.tsx

@@ -113,7 +113,14 @@ import {
 } from './msgContent';
 import { getMemberName, getMentionContent, trimReplyFromBody } from '../../utils/room';
 import { CommandAutocomplete } from './CommandAutocomplete';
-import { Command, SHRUG, TABLEFLIP, UNFLIP, useCommands } from '../../hooks/useCommands';
+import {
+  Command,
+  CommandError,
+  SHRUG,
+  TABLEFLIP,
+  UNFLIP,
+  useCommands,
+} from '../../hooks/useCommands';
 import { mobileOrTablet } from '../../utils/user-agent';
 import { useElementSizeObserver } from '../../hooks/useElementSizeObserver';
 import { ReplyLayout, ThreadIndicator } from '../../components/message';
@@ -665,16 +672,16 @@ export const RoomInput = forwardRef<HTMLDivElement, RoomInputProps>(
         const commandContent = commands[commandName as Command];
         if (commandContent) {
           // Fire-and-forget by design (the editor resets immediately for UX), but
-          // surface a rejection instead of failing silently. NOTE: /kick and /ban
-          // route through rateLimitedActions (utils/matrix.ts), whose to() helper
-          // swallows non-429 errors, so those two commands can still resolve even
-          // when the underlying kick/ban failed — this catch only covers errors
-          // that actually reject out of exe().
+          // surface a rejection instead of failing silently. /kick and /ban
+          // throw a CommandError whose message already names who and why
+          // (#216); anything else gets the generic sentence.
           commandContent.exe(plainText).catch((err) => {
             console.error(`Failed to run /${commandName} command:`, err);
             setToast(
               createErrorToast(
-                `The /${commandName} command failed. Please try again.`,
+                err instanceof CommandError
+                  ? err.message
+                  : `The /${commandName} command failed. Please try again.`,
                 Icons.Warning,
                 'Command failed',
               ),