0.28.0 — operational hardening (plan D1–D5): CI deploy gate, versioned images, rate limiting, resource limits, health probes

D1: deploy.sh CI gate — read-only SHA via git ls-remote, Gitea commit-status
    poll, portable mkdir deploy lock (macOS, no flock), TOCTOU guard, token
    passed via curl --config - (not argv), graceful misconfig tolerance.
D2: version-tagged images — OIKOS_VERSION=v$VERSION, keep-last-3 prune derived
    from 'docker compose config --images'; VERSION read after pull.
D3: per-IP rate limiting — new internal/httpapi/ratelimit.go (x/time/rate),
    rightmost-XFF, /healthz exempt, ctx-driven sweep; disabled by default.
D4: mem_limit/cpus on all 10 compose services.
D5: staleness-aware health probes — new internal/health package wired into
    scheduler (:8093) and notifier (:8094); nomos already had :8092.

Two /review passes hardened the deploy lock, TOCTOU guard, token hygiene,
and XFF handling.

plans/index.md

@@ -21,7 +21,7 @@ went sideways, open an investigation.
 | 2026-07-21 | [Frontend as OS + Apps — architecture audit & refactor](2026-07-21-frontend-os-apps-architecture.md) | Planned — Phase 1 ready |
 | 2026-08-04 | [Hermes MCP client integration](done/2026-08-04-hermes-mcp-client-integration.md) | Done — deployed |
 | 2026-08-05 | [Agent execution safety: QEMU guest agent gate + host-mutation guard](done/2026-08-05-agent-execution-safety-qemu-guest-agent-gate.md) | Done — implemented (1b9c761) |
-| 2026-08-05 | [Backend evaluation: architecture, security, and reliability improvements](2026-08-05-backend-evaluation-improvements.md) | Planned — 6 phases, security items first |
+| 2026-08-05 | [Backend evaluation: architecture, security, and reliability improvements](2026-08-05-backend-evaluation-improvements.md) | In Progress — Phase 0 (B) + Phase 2 (D1–D5) done; Phase 1 (C) pending |
 
 ## Done