Refactor: Remove redundant message state sync in ChatContainer

[shatfield4]

Pull Request Type

• ✨ feat
• 🐛 fix
• ♻️ refactor
• 💄 style
• 🔨 chore
• 📝 docs

Relevant Issues

resolves #4940

• Fixes the pending chat indicator (3 dot animation) rerendering/flickering when typing in the input while waiting for a
  response
• message state in ChatContainer was updating on every keystroke, causing unnecessary rerenders of the entire chat history including the pending indicator (pending indicator was the only visible bug but the entire history was actually rerendering)
• Removed redundant message state sync since PromptInput already maintains its own local state and now reads from DOM on submit instead

What is in this change?

Additional Information

• Sent regular chat and no longer rerenders 3 dot animation while message is pending
• Test STT in both auto submit and append mode
• Localstorage draft messages store properly
• Slash commands pops up on / typed into chat input
• Agent meny pops up on @ typed into chat input
• Pasted text pastes properly
• Undo/redo works properly
• Enter to submit chat, shift + enter creates new line

Developer Validations

• I ran yarn lint from the root of the repo & committed changes
• Relevant documentation has been updated
• I have tested my code functionality
• Docker build succeeds locally

[angelplusultra]

LGTM