Update spacing and width for end-aligned messages

[thatblindgeye]

Per chatbot sync call on 2-12-2026:

• Apply a max-width for end-aligned messages for all chatbot display modes (wide enough to not really matter in overlay/docked, try 475px as a starting point
• Apply margin/padding/inset start of spacer–-md for all chatbot display modes, for end-messages only

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Jira Issue: PF-3579