Review (nit 9, nit 4): when git could not list the tracked files the ratchet scanned nothing and
reported the tree clean; it now exits 2. A bare `detached-spawn: ok` with no reason passed; the
marker now counts only with a reason after the dash (every existing marker has one). The docstring
now lists the shapes it does not catch (PTY spawns, aliased imports, os.posix_spawn(setsid=True),
kw.setdefault("start_new_session", True)), and says that a group-killing timeout runs in the owner,
so an owner killed mid-wait leaves such a child to finish; the process_identity comment no longer
claims the ratchet keeps every detached spawn out.
Tests: a reasonless marker does not opt out; a tree git cannot list fails with exit 2. Both fail on
the prior ratchet.
kshitijk4poor
782c0f847c