POSIX fcntl locks are owned per (process, inode): closing any descriptor
for state.db releases every lock the process holds on that inode,
including the locks of an already-open SQLite connection. The
owner-only hardening cycle opened the live database and its -wal/-shm
read-only, fchmod'ed, and closed, so any process that already held a
connection (gateway, desktop hermes serve, dashboard share one) dropped
its live locks on every SessionDB init. A sibling process then took the
shared-memory DMS exclusively at its own close, checkpointed, and
unlinked the sidecars while long-lived holders kept the deleted inodes
open, tripping the deleted-WAL generation guard.
chmod(2) on the path never opens the file, so it cannot disturb locks.
The descriptor path remains only for first-time main-db creation, where
no locks can exist yet.
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