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

CHANGELOG.md

@@ -1,6 +1,29 @@
 <!-- xlate:verbatim-fences -->
 # Changelog
 
+## 0.1.8 — onboarding: keep the identity readable, refuse a full disk (2026-09-09)
+
+Three faults from one onboarding (env-dev-08, agent-managed, 2026-09-09), each of which sent the
+diagnosis somewhere other than the fault.
+
+- **The agent's read on the ziti identity now survives a tunneller rewrite.** `install.sh` granted it
+  with a POSIX ACL. `ziti-edge-tunnel` rewrites the identity file whenever the controller sends a config
+  update, and the rewrite drops the ACL — the agent had applied cleanly and was failing every tick six
+  minutes later. The durable grant is **group membership**: `install.sh` and the package's postinstall
+  now add `monky-deployd` to the identity file's group (`ziti`) when it exists, and a **default ACL** on
+  the identity directory carries the grant onto a freshly created file. The explicit ACLs stay.
+- **An unusable identity says so.** `openziti.load()` accepts an unreadable or malformed identity, logs
+  "configuration is invalid" at the C layer and hands back a context that fails LATER, 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 first, and names the real fault (absent, not
+  readable by this uid, or not JSON) before anything touches the mesh.
+- **A full disk is refused before the pull, and the right disk is measured.** The pre-flight ran only
+  when the bundle declared `disk_need_bytes`; a bundle without one sailed past it and 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. The pre-flight also 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
+  were on different filesystems — 93 GiB free where the agent looked, 2.8 GiB where the pull wrote.
+
 ## 0.1.7 — registry credential + a pull error you can read (2026-09-08)
 
 - **No hand `docker login` on a new box** (monky-design-docs !225, doc 24 §4a). A manifest entry marked