feat(tips): tip-chat keyboard on open + tip-only minimized send button

[bmc08gt]

What & why

Two tip-chat UX changes, plus a keyboard regression fix they surfaced.

1. Reopen the keyboard on message input (regression fix)

#1075 replaced the userState (Reading/Typing) model with the always-visible input and, in the process, turned OnStartMessageInput into a no-op and dropped the focusRequester.requestFocus() call. The event was still dispatched when returning from amount entry, but nothing acted on it — so the keyboard stopped reopening after sending cash from within a chat.

Restored via a transient State.messageInputRequested signal: OnStartMessageInput sets it; the bottom bar (co-located with ChatInput, so the focusRequester is attached) focuses the field, shows the keyboard, and dispatches OnMessageInputConsumed to clear it. It is state rather than a one-shot event because eventFlow is replay-0 — a request raised at open would be missed before the bar subscribes.

2. Open post-tip chats with the keyboard up

After completing a tip from the tip card, the chat now opens with the message input focused (same feel as returning from amount entry). A new openKeyboard flag on the Chat route (default false) is set only by the post-tip navigation (TipCardDecorator). Normal opens — tips list, deeplinks/notifications, contact DMs — stay keyboard-closed.

3. Minimized send button, tip chats only

Tip chats always show the compact dark symbol-only send button. The normal send flow keeps the expanded "Send $" presentation and only collapses to the symbol once the user starts typing.

Housekeeping

• docs: clarified that code/cash is the only main branch (repo origin/HEAD was unset, so tooling defaulted to a non-existent main).

Testing

• :messenger and :scanner compile clean.
• Not yet verified on-device — please sanity-check the two IME flows: returning from amount entry after a send, and a fresh post-tip chat open (keyboard up), while confirming normal chat opens stay closed.