Allow the chat input to be sent while the agent is mid-turn or awaiting
approval. The backend's prompt.submit busy-input policy already queues any
prompt that lands during a running turn (tui_gateway/server.py:_handle_busy_submit)
and drains it as the next turn, so the message is never dropped.
- ChatInputPolicy: pure, testable send/placeholder decision logic
- ChatScreen: canSend stays enabled while typing/approving; placeholder shows
'Queued — sends when agent is free' when text is present during a busy turn
- ChatInputPolicyTest: truth-table covering typing, approval-pending,
disconnected, empty, attachment, and slash-command cases
- strings: chat_input_placeholder_queue
Note: this supersedes the Genesi599 fork's approach (dispatchViaRpc('queue ...')),
which double-submits and relies on a 4018-prone command.dispatch path. The
backend-queued prompt.submit path is the correct, single-submission contract.
Co-authored-by: M57 <m57@hermes-control.app>
