docs: add Prometheus inventory export script for diagram/documentation pipeline

docs/architecture.md

@@ -95,6 +95,12 @@ Prometheus scrape targets indicate additional infrastructure outside the local C
 - `nix-cache`
 - `kuma.lan.ddnsgeek.com`
 
+## Runtime Inventory Input
+
+Prometheus runtime inventory snapshots are exported with `scripts/export_prometheus_inventory.py` and committed under `docs/runtime/`. The latest human-readable summary is in [docs/prometheus-inventory.md](prometheus-inventory.md).
+
+These artifacts are an observed-runtime input for architecture diagrams/docs and should be combined with repository configuration, not treated as sole source of truth.
+
 ## Assumptions / Unknowns
 
 The repository provides enough detail to infer **container-level architecture**, but not full **Proxmox host/VM topology**.

docs/prometheus-inventory.md

@@ -0,0 +1,38 @@
+# Prometheus Runtime Inventory
+
+This document is generated by `scripts/export_prometheus_inventory.py` from Prometheus runtime data. Commit the generated update whenever architecture/runtime inventory changes.
+
+## Usage
+
+Required:
+
+- `PROMETHEUS_URL`
+
+Optional:
+
+- `PROMETHEUS_TIMEOUT` (default: `10` seconds)
+- `PROMETHEUS_BEARER_TOKEN`
+- `PROMETHEUS_USERNAME`
+- `PROMETHEUS_PASSWORD`
+- `PROMETHEUS_VERIFY_TLS` (default: `true`)
+
+Run:
+
+```bash
+export PROMETHEUS_URL="https://prometheus.example.com"
+python3 scripts/export_prometheus_inventory.py --output-dir docs/runtime
+```
+
+## Outputs
+
+- Raw API snapshots: `docs/runtime/prometheus-targets.json`, query result snapshots, and optional label-query snapshots.
+- Normalized inventory: `docs/runtime/prometheus-inventory.json`
+- Human summary: `docs/prometheus-inventory.md` (this file)
+
+## Diagram/Docs pipeline note
+
+Treat Prometheus data as observed runtime telemetry. Do not infer placement/topology/network boundaries unless labels or other repo sources explicitly provide that information.
+
+## Status
+
+Inventory has not been generated in this environment because no `PROMETHEUS_URL` was provided for execution.