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>
tegwick
76c38e758c