chore(api,ci,docs,test): private-service schema, proto-check, fixups

Non-functional cleanups and contract/CI hardening around the
private-service work:

API schema (openapi.yml):
- Require a non-empty access_groups and mode=http when private=true,
  on both Service and ServiceRequest, mirroring
  validatePrivateRequirements. mode stays optional-but-constrained
  (empty defaults to http server-side), matching runtime.

CI (proto-version-check.yml):
- Cover renamed .pb.go files (read base via previous_filename).
- Match protoc-gen-go-grpc version headers (optional "- " prefix and
  -gen-go-grpc suffix) so grpc-generated files are in scope.

Docs / comments:
- Reword Config field docs to say defaults are applied at Server.Start
  (initDefaults), not New.
- Rename the obsolete --private-inbound flag to --private across
  comments and the proto doc.

Pre-existing test fixups surfaced by review:
- Repair the integration-tagged validate_session_test.go (SignToken
  signature growth + new Manager interface methods).
- Fix the CI-skip boolean precedence so Windows isn't skipped
  unconditionally.
- Guard the router.HTTPListener type assertion with comma-ok.

proxy/inbound.go

@@ -43,7 +43,7 @@ const privateInboundPortHTTPS = 443
 const privateInboundPortHTTP = 80
 
 // inboundManager wires per-account inbound listeners into the proxy
-// pipeline when --private-inbound is enabled. When disabled the manager
+// pipeline when --private is enabled. When disabled the manager
 // is nil and every method on *Server that touches it short-circuits.
 type inboundManager struct {
 	logger    *log.Logger
@@ -390,7 +390,7 @@ func (m *inboundManager) ListenerInfo(accountID types.AccountID) (InboundListene
 }
 
 // Snapshot returns the inbound listener state for every account that has
-// a live listener at call time. Empty when --private-inbound is off or
+// a live listener at call time. Empty when --private is off or
 // no accounts have come up yet.
 func (m *inboundManager) Snapshot() map[types.AccountID]InboundListenerInfo {
 	if m == nil {
@@ -513,7 +513,7 @@ func accountTunnelLookup(client *embed.Client) auth.TunnelLookupFunc {
 // peerstore lookup to every request's context before delegating to next.
 // Calling on the host-level listener is a no-op because that path never
 // installs this wrapper, so the existing behaviour stays byte-for-byte
-// identical when --private-inbound is off or the request didn't arrive
+// identical when --private is off or the request didn't arrive
 // on a per-account listener.
 func withTunnelLookup(next http.Handler, lookup auth.TunnelLookupFunc) http.Handler {
 	if lookup == nil {

proxy/inbound_test.go

@@ -140,7 +140,7 @@ func TestInboundManager_AddRouteAfterReady_RegistersDirectly(t *testing.T) {
 
 // TestPrivateCapability_DerivedFromPrivateOnly tests that the capability
 // bit reported upstream tracks --private exclusively. The previous
-// --private-inbound flag has been folded into --private.
+// --private flag has been folded into --private.
 func TestPrivateCapability_DerivedFromPrivateOnly(t *testing.T) {
 	tests := []struct {
 		name     string
@@ -319,7 +319,7 @@ func TestInboundManager_ListenerInfo(t *testing.T) {
 }
 
 // TestInboundManager_NilManagerSafe ensures the observability accessors
-// are safe to call when --private-inbound is off (nil manager).
+// are safe to call when --private is off (nil manager).
 func TestInboundManager_NilManagerSafe(t *testing.T) {
 	var mgr *inboundManager
 	_, ok := mgr.ListenerInfo("anything")

proxy/internal/debug/handler.go

@@ -131,7 +131,7 @@ func (h *Handler) SetCertStatus(cs certStatus) {
 
 // SetInboundProvider wires per-account inbound listener observability.
 // Pass nil (or skip the call) to keep the inbound section out of debug
-// responses on proxies that don't run --private-inbound.
+// responses on proxies that don't run --private.
 func (h *Handler) SetInboundProvider(p InboundProvider) {
 	h.inbound = p
 }

proxy/internal/tcp/router_test.go

@@ -1781,11 +1781,14 @@ func TestRouter_PlainHTTP_RoutesToPlainChannel(t *testing.T) {
 		}
 	}()
 
+	tlsListener, ok := router.HTTPListener().(*chanListener)
+	require.True(t, ok, "router.HTTPListener() must be the test's chanListener; the test relies on observing its channel directly")
+
 	select {
 	case conn := <-acceptDone:
 		require.NotNil(t, conn)
 		_ = conn.Close()
-	case <-router.HTTPListener().(*chanListener).ch:
+	case <-tlsListener.ch:
 		t.Fatal("plain HTTP request leaked into TLS channel")
 	case <-time.After(3 * time.Second):
 		t.Fatal("plain HTTP connection never reached plain channel")

proxy/lifecycle.go

@@ -20,14 +20,17 @@ import (
 type Config struct {
 	// ListenAddr is the TCP address the main listener binds. Required.
 	ListenAddr string
-	// ID identifies this proxy instance to management. Empty value lets
-	// New generate a timestamped default.
+	// ID identifies this proxy instance to management. Empty values are
+	// replaced with a timestamped default at Server.Start time (see
+	// initDefaults), not in New.
 	ID string
-	// Logger is the logrus logger used everywhere. Empty value falls back
-	// to log.StandardLogger().
+	// Logger is the logrus logger used everywhere. Empty values fall
+	// back to log.StandardLogger() at Server.Start time (see
+	// initDefaults), not in New.
 	Logger *log.Logger
 	// Version is the build version string reported to management. Empty
-	// becomes "dev".
+	// values are replaced with "dev" at Server.Start time (see
+	// initDefaults), not in New.
 	Version string
 	// ProxyURL is the public address operators use to reach this proxy.
 	ProxyURL string

proxy/server.go

@@ -281,7 +281,7 @@ func (s *Server) NotifyCertificateIssued(ctx context.Context, accountID types.Ac
 }
 
 // inboundListenerProto resolves the per-account inbound listener state for
-// the SendStatusUpdate payload. Returns nil when --private-inbound is off
+// the SendStatusUpdate payload. Returns nil when --private is off
 // or the account has no live listener so management treats the field as
 // absent.
 func (s *Server) inboundListenerProto(accountID types.AccountID) *proto.ProxyInboundListener {
@@ -528,7 +528,7 @@ func (s *Server) initManagementClient() error {
 }
 
 // initNetBirdClient builds the multi-tenant embedded NetBird client used
-// for outbound RoundTripping and (when --private-inbound is on) per-account
+// for outbound RoundTripping and (when --private is on) per-account
 // inbound listeners.
 func (s *Server) initNetBirdClient() {
 	s.netbird = roundtrip.NewNetBird(s.ID, s.ProxyURL, roundtrip.ClientConfig{