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)

template/Dockerfile

@@ -0,0 +1,23 @@
+FROM python:3.12-slim
+
+WORKDIR /app
+
+RUN apt-get update \
+    && apt-get install -y --no-install-recommends curl ca-certificates \
+    && rm -rf /var/lib/apt/lists/*
+
+COPY requirements.txt .
+RUN pip install --no-cache-dir -r requirements.txt
+
+COPY app/ ./app/
+
+RUN useradd --create-home --uid 1001 appuser \
+    && chown -R appuser:appuser /app
+USER appuser
+
+EXPOSE 8000
+
+HEALTHCHECK --interval=30s --timeout=5s --start-period=20s --retries=3 \
+    CMD curl -fs http://localhost:8000/health || exit 1
+
+CMD ["uvicorn", "app.agent:app", "--host", "0.0.0.0", "--port", "8000"]