feat: add /deploy-plugins webhook route + deploy-plugins script

CONTRIBUTING.md

@@ -14,7 +14,7 @@ repo, see [.agents/dev/CONTRIBUTING.md](.agents/dev/CONTRIBUTING.md).
   there); this repo is backend-only since the hexagonal refactor Phase 1
 
 ```bash
-# Start dependencies (Postgres + Redis). api/nomos require a shared bearer
+# Start dependencies (Postgres + Redis). api requires a shared bearer
 # token — no dev-open bypass — so set one even for local dev.
 OIKOS_MCP_BEARER_TOKEN=dev-token docker compose --profile dev up -d
 
@@ -46,7 +46,6 @@ before the split need one manual reinstall.
 
 ```
 cmd/oikos/          Single-binary entry point
-cmd/nomos/          Nomos MCP client gateway
 cmd/webhook/        Gitea deploy-webhook receiver (push-to-deploy on mac-mini)
 internal/           All Go packages
   core/             Hexagon core ([ADR 0016](docs/adr/0016-hexagonal-ports-adapters.md)):
@@ -79,7 +78,6 @@ compose/            Dockerfiles + Caddy config
 scripts/            Deploy, watchdog, rollback
 checks/             Host health-check scripts run over SSH by the scheduler
 tools/              Client auto-setup scripts (checks)
-nomos/              Nomos config, persona, skills
 .agents/            Agent instruction files + skills
 plans/              Design documents
 docs/adr/           Architecture decision records