remove hosts/ directory — single source of truth is inventory.yaml

- Delete cmd/oikos/build_hosts.go (generator no longer needed)
- Remove build-hosts subcommand from main.go
- Fix oikos homelab whoami: read from inventory.yaml instead of hosts/
- Update bootstrap.sh: identity check uses inventory.yaml
- Remove all 27 generated hosts/*.yaml files
- Update AGENTS.md and OIKOS.md to reference inventory.yaml only

AGENTS.md

@@ -16,13 +16,13 @@ Agent-facing instruction is separated from human content under `.agents/`:
 `.agents/domains/` holds the per-domain schemas
 ([knowledge](.agents/domains/knowledge/schema.md), [operations](.agents/domains/operations/schema.md)).
 The narrative wiki lives under `knowledge/wiki/`; the machine-readable substrate
-(`inventory.yaml`, `hosts/*.yaml`, `oikos/`) stays at the repo root.
+(`inventory.yaml` stays at the repo root.
 
 ## 1. Who you are
 
 Run `hostname` (Linux) or `scutil --get LocalHostName` (macOS), then read:
 
-    /opt/homelab-context/hosts/<your-hostname>.yaml
+    /opt/homelab-context/inventory.yaml
 
 That file tells you your role, your peers, what's mounted, and what services
 you host. If it does not exist, this client was not enrolled — stop and tell