feat: Add per-run tmpdir wipe and read-only fixture snapshots - #8
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Give each opted-in sandbox run a private workdir via mkdtemp, mount optional host fixtures as read-only copies, and always dispose the tree when the run settles so side effects cannot leak across runs.
fs.cp preserved host-pointing symlinks, so guest writes could mutate host files. Reject symlink hosts/trees, post-copy scan, regression tests, and accurate README (snapshots, not live mounts).
ThomasHartDev
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Each opted-in run gets a private mkdtemp workdir injected as
workdir, optional host fixtures snapshotted (content-copied) into the workspace as read-only files, and a guaranteed wipe when the result settles (ok, error, timeout, or throw).ephemeralFsworks on bothrunandrunInWorker;createEphemeralWorkspace/withEphemeralWorkspacecover standalone use.Symlink safety: host paths that are symbolic links, and directory trees that contain any symlink, are rejected with
FixturePathError. Defaultfs.cpwould preserve links and let a guest withfsallowed mutate host files through a recreated link under workdir. Mounts are content snapshots, not live mounts; host paths are never re-opened via links under the workspace.Fixture keys that try to escape the root (including keys that normalize to
.) are rejected before join. Linux hosts best-effort set the immutable bit; without it, mode-bit RO is advisory for same-uid guests (documented in README).Closes #7