v0.143.0 — guest RAM resize UI (R-24) — MinAgent: 0.90.0

The customer sees the guest's current memory + allowed range on the Rendszer settings
page and resizes it. The controller proxies + maps the agent's machine code to Hungarian;
the agent (felhom-agent v0.90.0) enforces every bound and applies live (no reboot).

agentapi: GuestMemory + ResizeMemory; ruled 412 -> *MemoryRefusedError (code+bounds);
pre-0.90 agent 404 -> typed *StatusError. Capability: FeatureGuestMemoryResize +
featureMinAgent 0.90.0 + a featureProbes row (type-asserts GuestMemory so the shared
SupportProber/netAgent are untouched).

UI (internal/web/system_memory_handlers.go, settings_system.html): "Szerver memoria (RAM)"
card + number input; POST /api/system/memory/resize -> capability gate -> agent -> flash.
JS confirm only on shrink. Code->Hungarian map; agent-outdated hides the control;
agent-unreachable falls back to the guest's /proc/meminfo. Agent English never shown raw.

Tests: agentapi (decode, 404, refusal-code, capability table) + web handler (success/
below_usage_floor/agent_outdated). Gates + go build/vet/test all pass.

controller/internal/agentapi/features.go

@@ -25,6 +25,10 @@ type Feature string
 // capability signal.
 const FeatureNetstorageVerify Feature = "netstorage_verify"
 
+// FeatureGuestMemoryResize is the guest RAM resize (agent v0.90.0, R-24): the resize endpoints
+// (GET/POST /guest/memory) shipped together, so GET /guest/memory IS the capability signal.
+const FeatureGuestMemoryResize Feature = "guest_memory_resize"
+
 // SupportState is a probe verdict. The zero value is SupportUnknown (fail-open: unknown never
 // refuses — the existing agent-error paths speak honestly when the agent is down).
 type SupportState int
@@ -67,14 +71,34 @@ var featureProbes = map[Feature]func(ctx context.Context, p SupportProber) error
 		_, err := p.NetVerifyStatus(ctx)
 		return err
 	},
+	// The memory-resize prober needs GET /guest/memory, not NetVerifyStatus. Rather than couple the
+	// shared SupportProber (and every unrelated prober/fake) to the memory surface, the probe
+	// type-asserts the ONE method it needs — the memory feature is only ever probed with a
+	// GuestMemory-capable prober (the web memAgent seam / *Client). A prober without it → a non-404
+	// error → SupportUnknown (fail-open), never a false "supported".
+	FeatureGuestMemoryResize: func(ctx context.Context, p SupportProber) error {
+		gm, ok := p.(interface {
+			GuestMemory(ctx context.Context) (GuestMemoryInfo, error)
+		})
+		if !ok {
+			return errNoMemoryProbe
+		}
+		_, err := gm.GuestMemory(ctx)
+		return err
+	},
 }
 
+// errNoMemoryProbe classifies to SupportUnknown (not a *StatusError 404), so a prober that cannot be
+// asked never reads as "unsupported".
+var errNoMemoryProbe = errors.New("agentapi: prober does not support the guest-memory probe")
+
 // featureMinAgent maps each coupled feature to the MINIMUM agent version that carries its coupled
 // semantics (the CHANGELOG `MinAgent:` header value). Used by Supports when the agent's version is
 // KNOWN (the v0.82.0 X-Felhom-Agent-Version channel) — a direct comparison, no probe traffic. A
 // feature missing here (or an unparseable table value) falls back to the probe.
 var featureMinAgent = map[Feature]string{
-	FeatureNetstorageVerify: "0.81.0",
+	FeatureNetstorageVerify:  "0.81.0",
+	FeatureGuestMemoryResize: "0.90.0",
 }
 
 // AgentVersionReporter is optionally implemented by a SupportProber (*Client is one): it reports