Add saiop-mcp-servers skill: least-privilege git/postgres/docker MCP setup, deferred SSH/pfSense

skills/saiop-infrastructure/saiop-mcp-servers/SKILL.md

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+---
+name: saiop-mcp-servers
+description: "MCP server setup for SAIOP (git, postgres read-only, docker read-only) — least-privilege patterns and what was deliberately NOT wired up."
+version: 1.0.0
+author: Claude Code (SAIOP ops session)
+license: MIT
+platforms: [linux]
+prerequisites:
+  env_vars: [MCP_POSTGRES_READONLY_PASSWORD]
+  commands: [uvx]
+metadata:
+  hermes:
+    tags: [SAIOP, MCP, security, least-privilege, postgres, docker, git]
+---
+
+# MCP servers on SAIOP (Phase 6.3)
+
+## When to use
+
+Adding or auditing MCP tool access for Hermes (Deployment Guide §6.3).
+
+## What's wired up and why
+
+- **git-mcp** (`uvx mcp-server-git -r /opt/ai-stack`) — all 12 tools enabled
+  (including commit/branch/checkout). Low risk: git is naturally revertible,
+  no host-level escalation path.
+- **postgres-mcp** (`uvx postgres-mcp --access-mode restricted`) — a
+  dedicated `mcp_readonly` Postgres role exists (SELECT-only, granted on
+  `saiop` + `netbox` DBs specifically, not the other app DBs). **Two
+  independent enforcement layers**: the role itself can't write (verified:
+  `DELETE` returns `permission denied`), and `--access-mode restricted`
+  blocks non-SELECT statements at the app layer too. Connection string goes
+  through the `DATABASE_URI` env var (checked the package source —
+  `os.environ.get("DATABASE_URI", args.database_url)`), not a CLI arg,
+  since CLI args are visible to any local user via `ps aux`.
+- **docker-mcp** (`uvx docker-mcp`) — **the npm/pip package itself has no
+  read-only mode.** It exposes `create-container` and `deploy-compose`
+  (full write/deploy) alongside `get-logs`/`list-containers`. Restricted via
+  Hermes's own `tools: {include: [...]}` allow-list in `config.yaml` to
+  just the two read-only tools — same enforcement mechanism already
+  field-verified for the Telegram platform-toolset restriction (a real
+  destructive command was confirmed blocked at the tool layer, not just
+  configured). **Do not change this to "all tools" without a deliberate
+  decision** — full Docker access would directly undermine the project's
+  core containment design (the `hermes` Linux user is deliberately denied
+  `docker compose`/restart-docker capability via scoped sudoers; an
+  unrestricted docker-mcp would hand that back through a side door).
+
+## What was deliberately NOT wired up
+
+- **SSH MCP** — no second system exists in this environment that needs SSH
+  access beyond the VM Hermes already runs on. The one genuinely sensitive
+  SSH target (the Proxmox hypervisor) is the project's hardest boundary —
+  don't wire SSH MCP access to it without the operator directly involved in
+  scoping exactly what it can reach.
+- **pfSense/MikroTik MCP** — no real device credentials exist in this
+  environment to configure them safely. Needs the operator to provide
+  scoped, read-only-by-default credentials first.
+
+## Useful commands
+
+```bash
+hermes mcp list                 # see all servers + tool-count summary
+hermes mcp test <name>          # verify a server connects and discover its tools
+```
+
+`hermes mcp add` has an interactive curses-based tool picker with no clean
+non-interactive path — for a scripted/repeatable setup, hand-edit
+`mcp_servers:` in `config.yaml` directly instead (schema:
+`{command, args, env, enabled, tools: {include: [...]}}`).