Adds the first local, same-host, kernel-namespace-only sandbox
extension: no SSH hop, no container runtime. Extends IsolationSpec.level
with "process", implements BwrapExtension (provision/wait_ready/
teardown) spawning bwrap with unshared user/mount/pid/ipc/uts/net
namespaces, registers ext.bwrap + profile.bwrap-local, and extends
manager._handle_from_status to carry pid/workspace_dir. Verified with a
live bwrap smoke run in addition to the mocked test suite.
T04 (reachability vs. the SSH-based glas-harness consumer contract)
deliberately left open pending glas-harness's harness contract.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Add workspace checkpoint API with SnapshotStore, extension hooks on
compose-ssh and saas-stub, manager orchestration, CLI/HTTP surface,
profile.compose-checkpoint, and docs/tests.
CoulombCore (92.205.130.254) authenticates as tegwick via id_ops in
ssh config, not root. Omit SANDBOXER_SSH_USER to let OpenSSH apply config;
set SANDBOXER_SSH_USER only to override.
