docs: v0.114.0 CHANGELOG (MinAgent header convention) + README NAS gate + CONTEXT + REUSE + coupled-feature rule in CLAUDE.md

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PSK5g6qYLknKj8u3QAFEr6

REUSE.md

@@ -110,6 +110,8 @@
 | `Client.FormatDisk` | controller/internal/agentapi/client.go | `(ctx, device, fstype, confirmed, durableID)` | ONLY format/wipe entry | Sentinels: `ErrNeedsConfirmation` (user-data, resubmit confirmed+durableID) / `ErrFormatRefused` (system/backup — operator opsign only). Agent re-checks role server-side |
 | `Client.EjectDisk` / `Decommission` / `AssignDisk` / `GuestAttach` / `ListCandidates` | controller/internal/agentapi/client.go | disk lifecycle | Delegate ALL disk ops to agent | Controller holds no Proxmox creds — never shell out to disk tools in-guest |
 | `Client.AddNetStorage/ListNetStorage/RemoveNetStorage` | controller/internal/agentapi/client.go | NAS mounts (A1) | Network storage | Password passes through to agent's 0600 cred file; controller NEVER persists it |
+| `agentapi.StatusError` | controller/internal/agentapi/client.go | `{Path, Code}` typed non-2xx GET error | Distinguishing HTTP statuses from transport errors (`errors.As`) | NEVER string-match agent error text — the capability probe keys on `Code==404` |
+| `SupportCache.Supports` / `Client.Supports` | controller/internal/agentapi/features.go | `(ctx, prober, Feature) SupportState` | Agent-capability gate for COUPLED features (route probe, TTL 5m) | 404 ⇒ No; transport/5xx ⇒ Unknown (NEVER refuse on Unknown). New coupled feature = new `featureProbes` row + gate call at the entry point + `MinAgent:` in the CHANGELOG header (publish-train-rules.md). Web layer: `Server.netFeatures` through the `netAgent` seam |
 
 ### Notifications / hub sync