Top-of-Feed Tips

What changed: Added configurable tips system that displays messages at the top of the conversation feed

Details:

• New u_0() component renders tips with color options: warning, error, or dimmed
• Tips cached in dynamic configs via A2Q config key
• Ma5() hook retrieves current tip using B2Q()
• Automatically invalidates cache when tip changes
• Default state: { tip: "", color: "dim" }
• Evidence: u_0() at line 424743, Ma5() at line 424769 in v2.0.10 (did not exist in v2.0.9)