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/worker.md

@@ -0,0 +1,22 @@
+---
+kind: Job
+name: worker
+runtime:
+  one_of: process
+  command: /usr/bin/python3 /opt/orca/jobs/worker.py
+timeout: 300s
+env:
+  QUEUE_URL: unix:///run/orca/alloc-worker/queue.sock
+  BATCH_SIZE: "100"
+  LOG_LEVEL: debug
+lifecycle:
+  post_start:
+    - /usr/local/bin/register-worker.sh
+  pre_stop:
+    - /usr/local/bin/drain-queue.sh
+---
+# Worker
+
+One-shot batch worker that processes items from a queue. Runs once,
+exits on completion or after 300s timeout. Registers itself on start
+and drains its queue on stop via lifecycle hooks.