transition precondition enforcement + thin-client context poller

Plan #3 at 100%. Last three items resolved:

1. Transition precondition enforcement (Phase 5):
   - no-inbound-edges: blocks destroy when relationships exist
   - backups-verified, secrets-revoked, ingress-dns-removed: checks attrs
   - age-key-enrolled-if-needed, mesh-joined-if-needed: workstation checks
   - health-check-answering: verifies entity_status health
   - doc-page-complete: requires at least one linked document
   - Soft preconditions (inventory-entry, cancelled-note, etc.): operator
     confirmed via transition request itself
   - Parses {requires: [check-name]} from lifecycle_defs.transitions JSONB

2. bootstrap.sh: already thin-client (fetches only agent files, no git clone,
   calls POST /clients/enroll, embeds context poller)

3. tools/context-poller.sh: standalone version — polls GET /clients/{slug}/context,
   applies file/tool/sops deltas, re-runs changed setup scripts

plans/2026-07-07-client-lifecycle-in-go.md

@@ -1,6 +1,6 @@
 # Plan: Client lifecycle — enrollment through deprecation in Oikos Go
 
-**Status:** Done (2026-07-08) — API surface complete. All endpoints, lifecycle transitions, provision flow implemented and tested (324-line e2e test). Remaining: bootstrap.sh rewrite + context-poller.sh (thin-client distribution, tracked as follow-up).
+**Status:** Done (2026-07-08) — full API surface + transition preconditions + thin-client distribution.
 
 ## Goal