Add community node protocol spec, Agent Skills, and make the failing tests hermetic

Community nodes (Phase 1 of plan.md): the protocol specification in
services/nodes/spec.py as the single source of truth, GET /nodes/spec.json,
a generated protocol docs page, the Community nodes API docs group, and the
implementation plan plus the residential proxy research. The no-open-proxy rule
is enforced in the spec (open_proxy cannot be set).

Agent Skills: register the Skills API docs group, cascade skills on account
deletion, add the nested CLAUDE.md, README and routes docs, and cover the
parser, the fetcher (end to end against a mock origin), the data layer and the
routes with 73 unit and 16 api tests.

Tests made hermetic with the repo's existing patterns instead of ambient
environment: embeddings tests set OPENROUTER_API_KEY via monkeypatch, the
workspace tests install FakeBackend via runtime.set_backend, and the skills
install tests use run_async. DockerCliBackend now returns 127 (command not
found) when the CLI is missing instead of raising FileNotFoundError, so a host
without docker answers with a clean error rather than a 500. The Providers tab
empty state no longer names the Model routes tab.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

docker-compose.yml.bak-20261008

@@ -0,0 +1,56 @@
+name: devplace
+
+services:
+  app:
+    build:
+      context: .
+      dockerfile: Dockerfile
+    restart: unless-stopped
+    env_file:
+      - .env
+    user: "${DEVPLACE_UID:-1000}:${DEVPLACE_GID:-1000}"
+    working_dir: /app
+    environment:
+      HOME: /app
+      PYTHONDONTWRITEBYTECODE: "1"
+      # Pinned regardless of .env: the container always binds 10500 internally
+      # (Dockerfile CMD, nginx upstream). DEVPLACE_PORT is the bare-metal
+      # `make dev`/`make prod` knob; the externally reachable port is `PORT`.
+      DEVPLACE_PORT: "10500"
+    volumes:
+      - .:/app
+    expose:
+      - "10500"
+    networks:
+      - appnet
+    healthcheck:
+      test: ["CMD", "curl", "-f", "http://localhost:10500/"]
+      interval: 30s
+      timeout: 10s
+      retries: 3
+      start_period: 120s
+      start_interval: 2s
+
+  nginx:
+    build:
+      context: .
+      dockerfile: nginx/Dockerfile
+    restart: unless-stopped
+    ports:
+      - "127.0.0.1:${PORT:-10500}:80"
+    environment:
+      NGINX_CACHE_ENABLED: "${NGINX_CACHE_ENABLED:-false}"
+      NGINX_CACHE_MAX_SIZE: "${NGINX_CACHE_MAX_SIZE:-1g}"
+      NGINX_MAX_BODY_SIZE: "${NGINX_MAX_BODY_SIZE:-50m}"
+    volumes:
+      - ./devplacepy/static:/app/static:ro
+      - ${DEVPLACE_DATA_DIR:-./data}/uploads:/data/uploads:ro
+    depends_on:
+      app:
+        condition: service_healthy
+    networks:
+      - appnet
+
+networks:
+  appnet:
+    driver: bridge