Slash-command replies and the echoed /setup command are persisted to session
history so they render in the transcript, but they are UI chatter the user
never meant as conversation. They were sent to the model on the next turn,
which then commented on '/setup ...' and exposed transient values (e.g. the
Copilot device user_code) to the LLM.
- get_context_messages() (the LLM-API view) now skips messages tagged
metadata.source == 'slash'. Display/history-load paths use raw history and
are unaffected.
- slashCommands.js tags the echoed user command with source:'slash' too (the
assistant replies already carried it); the user line was the one untagged
path that still reached context.
Fixes#2634.