FS Observation Policy
Domain: Configuration
Motivation
dsh-fs-observation-policy makes filesystem tools require an agent to read a file before overwriting or editing it, and rejects a mutation when the file changed since that read. It needs no configuration and injects no service — it listens for the fs/* events the tools dispatch. Reading a missing path authorizes guarded creation, and a resumed session starts with no observations, so it must re-read targets again.
Concrete Example
An edit without a prior read fails with FS_NOT_OBSERVED (edit requires reading "<path>" first); a stale edit fails with FS_STALE_VERSION and the remedy to re-read.
Analogy
It is a read-before-write gate that also detects if the file moved while you were typing.