feat(telemetry)!: promote to v1.0.0 — named shutdown errors per provider, Go 1.26

Label each provider shutdown failure with its signal name (trace/metric/log).
Errors remain joined via errors.Join; individual causes still unwrappable.
Go directive bumped from 1.25 to 1.26. API committed as stable.

telemetry.go

@@ -105,15 +105,30 @@ func New(ctx context.Context, cfg Config) (func(context.Context) error, error) {
 	global.SetLoggerProvider(lp)
 
 	shutdown := func(ctx context.Context) error {
-		return errors.Join(
-			tp.Shutdown(ctx),
-			mp.Shutdown(ctx),
-			lp.Shutdown(ctx),
-		)
+		var errs []error
+		if err := tp.Shutdown(ctx); err != nil {
+			errs = append(errs, &providerErr{"trace", err})
+		}
+		if err := mp.Shutdown(ctx); err != nil {
+			errs = append(errs, &providerErr{"metric", err})
+		}
+		if err := lp.Shutdown(ctx); err != nil {
+			errs = append(errs, &providerErr{"log", err})
+		}
+		return errors.Join(errs...)
 	}
 	return shutdown, nil
 }
 
+// providerErr labels a shutdown error with the provider name.
+type providerErr struct {
+	provider string
+	err      error
+}
+
+func (e *providerErr) Error() string  { return "telemetry: " + e.provider + " provider shutdown: " + e.err.Error() }
+func (e *providerErr) Unwrap() error  { return e.err }
+
 // newResource builds an OTel resource with service identity and environment attributes.
 func newResource(cfg Config) *resource.Resource {
 	r, _ := resource.Merge(