v3.9.1

Sweeps get the superseded check: a sweep no longer ships a fix a live session already made.

Fixed

• A sweep no longer ships a fix a live session already made (ledger lib/autofix-sweep.sh:747). 3.9.0 added the superseded check to spot runs only. A sweep now applies the same check, against the commit it was cut from, at three points. When an entry is handed to a fixer (launcher A's loop, launcher B's autofix next), an entry whose cited code changed on the landing branch is skipped without a paid fixer. Before an approved fix is committed, a change made while its fixer ran skips it. Before ship, a committed fix whose code changed since is dropped: the commit stack is rebuilt without its commit, a later commit that no longer applies without it goes too, and the rebuilt stack still faces the ship-time test run. A rebuilt stack that fails those tests ends failed with its branch kept, with no ship retries. Dropped entries show as skipped with the reason in the PR table, stay open in the ledger, and are not closed by the PR. A sweep whose every fix was dropped ends stale with no PR and still queues the next batch of a chain. Launcher B's other commands (search, test, verify, release, brief) never move past the entry a fixer is working on. A ship retry keeps its stack as it is.
• A readiness timing test no longer fails on a loaded host. "a base run that passed only on its re-run records one run's time" allowed at most 3 s for a 2 s run, and the full suite once recorded more. It now sleeps 3 s and asserts under 6 s (two runs would take 6+).