Ask mode

A thread can run in Ask mode: read-only questions about the repo, answered from the code index and shared memory. It never spawns a worktree, never calls tools, and never counts against the daily budget. Create one from the sidebar caret, or turn it on from the overflow menu (which clears Teach, which conflicts). The composer then hides permission, Build, Best of N, and attach. Answers prefer the on-device fm CLI, then the provider in print mode, then a retrieval-only pack if neither is available. Start work turns Ask off and, when Isolate new threads is on, arms a worktree for the next turn.