docs: generate Prometheus-driven monitoring docs and Mermaid diagrams

docs/architecture.md

@@ -113,3 +113,40 @@ Unknowns (left intentionally as placeholders):
 - **Inter-host VLAN/subnet layout beyond Docker bridges:** _unknown from repo contents._
 
 If you want, this section can be replaced with a concrete Proxmox topology once you add an inventory source (e.g., Terraform, Ansible inventory, or a diagram export).
+
+## Runtime visibility from Prometheus
+
+<!-- BEGIN GENERATED PROMETHEUS SECTION -->
+
+Prometheus inventory provides **observed runtime coverage** of scrape targets. It complements (but does not replace) declared architecture in Compose files and static docs.
+
+- Inventory timestamp: `2026-04-13T06:36:45Z`
+- Observed jobs: `8`
+- Observed instances: `19`
+- Observed services (label-derived): `1`
+
+### Observed monitoring view
+
+| job | targets | unhealthy |
+| --- | --- | --- |
+| container-updates | 2 | 0 |
+| kuma | 2 | 0 |
+| node | 7 | 0 |
+| pihole | 1 | 0 |
+| prometheus | 1 | 0 |
+| proxmox-storage | 2 | 0 |
+| telegraf | 2 | 0 |
+| traefik | 2 | 0 |
+
+### Data sources
+
+- `docs/runtime/prometheus-inventory.json` (normalized runtime export)
+- Prometheus scrape metadata (`targets` + label sets)
+- Existing repository architecture docs for declared topology
+
+### Notes from inventory
+
+- The `up` query indicates scrape success from Prometheus perspective only.
+- Use static repository architecture docs and deployment configs with this runtime export for complete diagrams.
+
+<!-- END GENERATED PROMETHEUS SECTION -->