feat: initial harness spec v1.0.0 + reference template

Adds the normative contract every platform agent must conform to, plus a
working reference template under template/ that ticks every box out of
the box.

Spec is derived from the production agents shipped in
cjot-backstage-az/agents/ on branch sandbox/jonathan:
  - agent-registry, agent-factory, decomposer, discovery-agent,
    golden-path, modernization-factory, modernization-factory-v2,
    policy-transformer, scaffold-agent, support-intake-agent, the-watcher

Contents:
  - SPEC.md          normative contract (13 sections + conformance checklist)
  - CHANGELOG.md     spec versioning (1.0.0)
  - docs/
      registration.md   self-registration with the agent-gateway
      observability.md  OTel logs/metrics/traces wiring
      manifest.md       /.well-known/agent.json schema + AgentSkill
                        serialisation (pydantic vs protobuf)
      kubernetes.md     k8s deployment shape, mandatory cross-refs,
                        per-namespace agents, resource sizing
      deployment.md     .image-version, ACR build, deploy scripts, rollback
      deviations.md     tracked debts against the spec
  - template/
      .env.local.example, .gitignore, .image-version (0.1.0),
      Dockerfile (python:3.12-slim, non-root UID 1001, HEALTHCHECK),
      requirements.txt (harness floor + optional LLM stack),
      app/agent.py (Starlette entry, lifespan + self-registration,
                    defensive _skill_dict for pydantic vs protobuf),
      app/logging_setup.py (canonical OTel log bridge — copy verbatim),
      app/metrics.py (meter + example counter/histogram),
      app/skills.py (AGENT_CONFIG + AgentSkill list),
      k8s/configmap.yaml + deployment.yaml (Deployment + Service,
                                            OTel annotations + 6-var env block,
                                            agents-sa + agents-kv-spc bindings),
      scripts/deploy.sh (auto-bump + az acr build + apply + rollout),
      scripts/full-deploy.sh (preflight + deploy + post-deploy smoke),
      scripts/deploy-local.sh (docker/podman + .env.local)

CHANGELOG.md

@@ -0,0 +1,34 @@
+# Changelog — agent-harness-spec
+
+All notable changes to the spec are recorded here. The spec follows [semver](https://semver.org/).
+
+## [1.0.0] — 2026-06-09
+
+Initial draft derived from the production agents shipped in `cjot-backstage-az/agents/` on branch `sandbox/jonathan`:
+
+- `agent-registry` (FastAPI, registry/gateway)
+- `agent-factory`
+- `decomposer`
+- `discovery-agent`
+- `golden-path`
+- `modernization-factory` (v1)
+- `modernization-factory-v2`
+- `policy-transformer`
+- `scaffold-agent`
+- `support-intake-agent` (FastAPI, intake)
+- `the-watcher`
+
+Codifies:
+
+- Mandatory `app.agent:app` Starlette entry point
+- `GET /health` and `GET /.well-known/agent.json` contract
+- Self-registration with the agent-gateway via `POST /agents/register-url` (3×5s retry budget)
+- OTel operator-driven SDK injection + the six standard env vars (`OTEL_SERVICE_NAME`, `OTEL_RESOURCE_ATTRIBUTES`, `OTEL_LOGS_EXPORTER`, `OTEL_METRICS_EXPORTER`, `OTEL_METRIC_EXPORT_INTERVAL`, `OTEL_SEMCONV_STABILITY_OPT_IN`)
+- Canonical `app/logging_setup.py` bridge (root logger → `LoggerProvider`)
+- `app/metrics.py` shape (`metrics.get_meter(name, version)` + module-scope instruments, `agent.<type>.*` naming)
+- LangChain instrumentation via `LangChainInstrumentor().instrument()`
+- Container shape (`python:3.12-slim`, non-root UID 1001, HEALTHCHECK)
+- Kubernetes shape (namespace `agents`, ServiceAccount `agents-sa`, `agents-kv-spc` SPC at `/mnt/secrets-store`, named `http` port, OTel inject annotations)
+- `.image-version` file + `scripts/deploy.sh` / `full-deploy.sh` / `deploy-local.sh` cadence
+
+Defensive serialisation for `a2a.types.AgentSkill` (pydantic vs protobuf) is mandated in §6 to avoid the `model_dump()` regression observed in `policy-transformer` 1.0.2 → 1.0.3.