clockclock1/dsh-nitro

Per-session fast-delivery mode from the composer. New conversations start enabled; switching is refused while that conversation is running, and a read-only session-header badge shows on/off during a run. One switch drives three subsystems: a circuit breaker that short-circuits test and build commands instead of running them, an apply_patch tool that writes SEARCH/REPLACE hunks atomically (all anchors must match or nothing is written), and a dehydrator that trims terminal output to a pass line or the last 15 error lines.