fix(onboarding): identity read that survives a rewrite, disk refused before the pull — 0.1.8

Three faults from one agent-managed onboarding (env-dev-08, 2026-09-09), each of which pointed
the diagnosis away from the actual fault.

1. install.sh granted the agent's read on the ziti identity with a POSIX ACL. ziti-edge-tunnel
   rewrites that file on a controller config update and the rewrite drops the ACL: the agent
   applied cleanly at 01:21 and was failing every tick by 01:32. Group membership survives the
   rewrite (the file stays ziti:ziti 0640), so install.sh and the package postinstall now add
   monky-deployd to the `ziti` group, and a default ACL on the identity directory carries the
   grant onto a newly created file. The explicit ACLs stay for the boxes that need them.

2. openziti.load() accepts an unreadable or malformed identity: the C SDK logs "configuration is
   invalid" and returns a context that only fails at dial, as a bare TypeError, which the
   transport reported as a missing intercept or a policy gap. The SDK transport now reads and
   parses the identity itself and names the real fault first.

3. The disk pre-flight ran only when the bundle declared disk_need_bytes, so a bundle without one
   died mid-pull with containerd's "no space left on device" — which reads as a registry fault.
   A bundle that declares no size now has to clear the headroom floor, and the pre-flight measures
   containerd's root as well as the docker data-root: docker 29 keeps image layers in the
   containerd image store, and on env-dev-08 those sat on different filesystems (93 GiB free where
   the agent looked, 2.8 GiB where the pull wrote).

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KLB7jieMNRkTsJ2epr4Ds1

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "monky-deployd"
-version = "0.1.7"
+version = "0.1.8"
 description = "Monky backend pull agent: checkin -> bundle -> lease -> OpenBao -> docker compose -> report, over the ziti mesh (MONKY-ADR-0028)"
 readme = "README.md"
 requires-python = ">=3.12"