* feat(acp): compact Grok, OpenCode and OMP chats
* test(acp): expect Grok compaction capability
* fix(chat): keep skipped compaction outcomes visible across history pages
* fix(acp): a signed-out /compact reports not signed in, as a send does
A /compact the agent refused for sign-in now records the same notSignedIn
fact as an ordinary send, so the chat shows sign-in guidance and the next
send starts a new agent that reads the new login.
* refactor(acp): keep the timeline translator under its line limit after main's growth
Main's OMP per-channel message identity grew acp-timeline-translator.ts past
max-lines with this PR's compaction handling. The running compaction's frame
folding moves beside its ending in acp-compaction-turn.ts, and the
compacting-prompt lookup into AcpPromptTurns; behaviour is unchanged.
