docs(P03): full-stack examples — 5 jobspecs + rendered artifacts + walkthrough

P03 — full-stack example with ingress configured (REQ-094; gate C-20).

examples/full-stack/:
- web-app.md: kind Service, process runtime, 3 replicas, Unix socket
  (default R-007), rolling update, constraints (node.role==web),
  affinity (zone==a weight 80), lifecycle hooks (post_start/pre_stop).
- api.md: kind Service, process runtime, 2 replicas, TCP opt-in
  (service.bind: 127.0.0.1, R-007), canary update with manual promote,
  constraints (node.role==api, node.cpus>=2), env vars.
- worker.md: kind Job, process runtime, one-shot, timeout 300s, env
  vars, lifecycle hooks (register/drain).
- log-shipper.md: kind Service (DaemonSet workaround — parser gap),
  process runtime, constraints (node.role==logs), env vars. Notes the
  v0.9 parser gap (schedule: block not wired) in a callout.
- postgres.md: kind Service, process runtime, 1 replica, blue-green
  update, volumes with replication (replicate:peer-b,peer-c via
  Syncthing), constraints (node.role==db, node.cpus>=4, node.memory>=8192).
- rendered/: Traefik dynamic YAML (web-app, api) + systemd units
  (web-app, api, log-shipper) showing what Orca generates on target nodes.
- README.md: end-to-end walkthrough (init -> node join -> capacity set
  -> ns create -> job run -> list --watch -> inspect rendered -> verify
  ingress -> drain/rollback). Cross-links to docs/ingress.md.
- examples_test.go: Go test that parses + validates all 5 jobspecs
  against the current parser and schema validators (gate C-20).

All 5 jobspecs pass jobspec.ParseFile + schema.ValidatorFor(kind).

---ci---
project: orca
phase: 3
milestone: v0.10
status: execute
---/ci---

examples/full-stack/api.md

@@ -0,0 +1,43 @@
+---
+kind: Service
+name: api
+count: 2
+runtime:
+  one_of: process
+  command: /usr/bin/api-server --listen 127.0.0.1:9090
+ports:
+  - name: api
+    port: 9090
+restart:
+  mode: service
+  attempts: 3
+  delay: 5s
+update:
+  strategy: canary
+  canary: 1
+  max_parallel: 1
+  auto_promote: false
+  min_healthy_time: 30s
+  healthy_deadline: 5m
+service:
+  name: api
+  port: 9090
+  bind: 127.0.0.1
+health:
+  check_type: http
+  interval: 10s
+  timeout: 2s
+  unhealthy_threshold: 3
+constraints:
+  - node.role == "api"
+  - node.cpus >= 2
+env:
+  DB_HOST: postgres
+  DB_PORT: "5432"
+  LOG_LEVEL: info
+---
+# API Server
+
+Backend API service binding to 127.0.0.1:9090 (TCP opt-in, R-007).
+Canary update strategy with manual promote. Two replicas with CPU
+constraint (>= 2 vCPUs) and API-role node selection.