Remote Control: /help (and other terminal-only commands) shown in slash menu but rejected

Environment: Claude Code web app driving a Remote Control session.

Problem: The composer placeholder reads "Type / for commands", and /help is offered/accepted as input — but running it returns:

/help isn't available over Remote Control.

Terminal-only commands (e.g. /help, and likely /config, /fast, status-line, etc.) are surfaced in the UI as if available, then rejected at execution time.

Expected: Commands that are not supported over Remote Control should be hidden/disabled from the slash-command surface in that session type, rather than shown and then erroring on use.

Actual: They appear available, accept input, and fail only on execution — a confusing dead end.

Repro:

1. Open the web app and start a Remote Control session.
2. In the composer, send /help.
3. Observe the "isn't available over Remote Control" rejection.

Suggested fix: Filter the slash-command list (and/or placeholder hint) by session capability so Remote Control sessions only advertise commands they can actually run.