Resolve Client.Go-004..010 code-review findings

Client.Go-004: ran gofmt on alarms_test.go and galaxy_test.go; the tree is
now gofmt-clean.

Client.Go-005/009/010: migrated Dial/DialGalaxy off the deprecated
grpc.DialContext/WithBlock to grpc.NewClient via a shared dial helper, with
a DialTimeout-bounded readiness probe to keep fail-fast semantics; shared
callContext deadline arithmetic; updated the stale Dial doc comment. Test
harnesses use passthrough:///bufnet for the NewClient default-scheme change.

Client.Go-006: added GatewayError.Code() and an IsTransient(err) helper so
callers can classify transient gRPC failures.

Client.Go-007: newCorrelationID no longer returns an empty id when
crypto/rand fails — it falls back to a non-empty time+counter id.

Client.Go-008: added coverage_test.go for transport-credential resolution,
callContext deadline arithmetic, and native value/array edge kinds.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

clients/go/mxgateway/galaxy.go

@@ -2,7 +2,6 @@ package mxgateway
 
 import (
 	"context"
-	"errors"
 	"io"
 	"time"
 
@@ -56,39 +55,13 @@ type GalaxyClient struct {
 
 // DialGalaxy opens a gRPC connection to the gateway for the Galaxy Repository
 // service. It applies the same authentication metadata, transport security,
-// and dial-timeout behavior as Dial.
+// lazy connection, and DialTimeout-bounded readiness probe as Dial.
 func DialGalaxy(ctx context.Context, opts Options) (*GalaxyClient, error) {
-	if opts.Endpoint == "" {
-		return nil, errors.New("mxgateway: endpoint is required")
-	}
-
-	dialCtx := ctx
-	cancel := func() {}
-	if opts.DialTimeout > 0 {
-		dialCtx, cancel = context.WithTimeout(ctx, opts.DialTimeout)
-	} else if _, ok := ctx.Deadline(); !ok {
-		dialCtx, cancel = context.WithTimeout(ctx, defaultDialTimeout)
-	}
-	defer cancel()
-
-	transportCredentials, err := resolveTransportCredentials(opts)
+	conn, err := dial(ctx, opts)
 	if err != nil {
 		return nil, err
 	}
 
-	dialOptions := []grpc.DialOption{
-		grpc.WithTransportCredentials(transportCredentials),
-		grpc.WithUnaryInterceptor(unaryAuthInterceptor(opts.APIKey)),
-		grpc.WithStreamInterceptor(streamAuthInterceptor(opts.APIKey)),
-		grpc.WithBlock(),
-	}
-	dialOptions = append(dialOptions, opts.DialOptions...)
-
-	conn, err := grpc.DialContext(dialCtx, opts.Endpoint, dialOptions...)
-	if err != nil {
-		return nil, &GatewayError{Op: "dial", Err: err}
-	}
-
 	return NewGalaxyClient(conn, opts), nil
 }
 
@@ -239,18 +212,5 @@ func (c *GalaxyClient) Close() error {
 }
 
 func (c *GalaxyClient) callContext(ctx context.Context) (context.Context, context.CancelFunc) {
-	timeout := c.opts.CallTimeout
-	if timeout == 0 {
-		timeout = defaultCallTimeout
-	}
-	if timeout < 0 {
-		return ctx, func() {}
-	}
-	if deadline, ok := ctx.Deadline(); ok {
-		timeoutDeadline := time.Now().Add(timeout)
-		if deadline.Before(timeoutDeadline) {
-			return ctx, func() {}
-		}
-	}
-	return context.WithTimeout(ctx, timeout)
+	return callContext(ctx, c.opts.CallTimeout)
 }