Follow-up to the agent reply bar fix: instead of special-casing the
agent branches, Post now derives isReplyPost once, renders ReplyBar in
a single place around whichever body it picked, and passes isReplyPost
down to Body and AgentPost. This also covers Calls and burn-on-read
reply bodies, lets agent markdown size images for the narrower reply
column, and trims ReplyBar to its three styling props.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VETkdQ3i2WN1XbpyKxjKUy
6f49d89c06