Three independent bugs fixed:
1. IM channels were sending raw <attachments>/<reactions>/<speech> tag blocks
alongside file attachments. Now ExtractAssistantOutputs strips these tags
before building the outbound channel message.
2. WebUI rendered these tags as markdown after page refresh. Now
extractMessageText strips agent tags for non-user messages.
3. WebUI lost attachment blocks after refresh because convertMessagesToChats
did not call buildAssetBlocks when merging assistant messages into a
pending tool-call group. Also made LinkOutboundAssets session-aware so
assets are linked to the correct assistant message.
Acbox
f1dd30a388