feat: Multiline chat input with auto-resize

[sre-helmcode]

Summary

Replace the single-line <input> element in the chat with a <textarea> that supports line breaks and grows dynamically with the text content.

Current State

• The chat input is a standard <input> element (TeamMonitorPage.tsx, lines 622-636)
• Does NOT support line breaks — even Shift+Enter does nothing useful
• Pasting multiline text strips all newlines
• Fixed single-line height regardless of content
• Enter sends the message, Shift+Enter is handled but has no effect

Proposed Solution

1. Replace <input> with <textarea> in TeamMonitorPage.tsx
2. Auto-resize behavior:
   • Default: 1 line height (same as current input)
   • Grows as user types or pastes multiline content
   • Max height: ~6 lines (~150px), then scrollbar appears
   • Shrinks back when text is deleted
3. Keyboard handling:
   • Enter → sends the message (existing behavior preserved)
   • Shift+Enter → inserts a newline
4. Preserve existing styles (dark theme, border colors, error states, disabled state)
5. Implementation approach:

   <textarea
     ref={textareaRef}
     value={chatMessage}
     onChange={(e) => {
       setChatMessage(e.target.value);
       autoResize(e.target);
     }}
     onKeyDown={(e) => {
       if (e.key === 'Enter' && !e.shiftKey) {
         e.preventDefault();
         handleSend();
       }
     }}
     rows={1}
     style={{ maxHeight: '150px', overflowY: 'auto' }}
     className="flex-1 rounded-lg border bg-slate-900 px-3 py-2 text-sm text-white resize-none ..."
   />

Affected Files

• src/pages/TeamMonitorPage.tsx — Lines 622-636 (input element)

Acceptance Criteria

• Input accepts multiline text
• Shift+Enter inserts newline
• Enter sends message (unchanged behavior)
• Input grows dynamically up to ~6 lines
• Input shrinks when text is removed
• Scrollbar appears when exceeding max height
• Pasting multiline text preserves line breaks
• Existing styles and states (error, disabled) preserved
• resize: none to prevent manual resize handle

[sre-helmcode]

Implemented and merged to main (3c24b07). Textarea with auto-resize (1-6 lines, 150px max), Shift+Enter for newlines, Enter to send, aria-label for accessibility, auto-resize on send failure recovery.