Multiple concurrent Claude sessions (and the scheduled-task sync) were
stepping on each other's git state. sync.sh now takes an atomic mkdir
lock in .git/ around the whole run (stage/commit/fetch/rebase/push +
vault), exits 75 (EX_TEMPFAIL = deferred) on contention instead of
racing, and reclaims stale/dead-owner locks with a re-verify-before-clear
guard (closes two TOCTOU races caught in review). /save now mandates
per-session-unique log filenames (never the bare YYYY-MM-DD-session.md).
Docs updated for the lock + deferred-exit semantics.
Note: git add -A is still the catch-all sweep; full per-session commit
isolation and routing /scc + /checkpoint through the lock are follow-ups.
Mike Swanson
6b0ce9aa04