feat: up/down arrow key navigation for input history in chat

[Harigithub11]

Summary

The chat input should support navigating previously sent messages using ArrowUp and ArrowDown — similar to how a terminal shell works.

Current Behavior

When no @ mention dropdown is open, arrow keys have no effect on the input field.

Expected Behavior

• ArrowUp: load the previous sent message into the input. On first press, save the current draft so it can be restored.
• ArrowDown: move forward through history. Once past the last entry, restore the saved draft.
• Typing while navigating history should exit history mode.
• Consecutive duplicate messages should not be stored twice.

Where to Look

Primary file: app/(main)/chat/[chatId]/components/MessageComposer.tsx

• handleKeyPress — already handles ArrowUp/Down for @ mention autocomplete. Add history navigation in the else branch when no mention dropdown is open.
• The composer.unstable_on("send", ...) handler — this is where the composer clears after a message is sent. Save the sent message to history here before clearing.
• handleMessageChange
• — fires on every keystroke. Reset history navigation state here when the user types manually.

You'll need to track: the list of sent messages, the current position in that list, and the draft that was in the input before the user started navigating back.

Files to Change

File	What changes
app/(main)/chat/[chatId]/components/MessageComposer.tsx	Add history state, capture sent messages, handle ArrowUp/Down navigation

No new dependencies required.