refactor(desktop): split kernel_commands/pipeline_commands into modules, add SaaS client libs and gateway modules

Split monolithic kernel_commands.rs (2185 lines) and pipeline_commands.rs (1391 lines)
into focused sub-modules under kernel_commands/ and pipeline_commands/ directories.
Add gateway module (commands, config, io, runtime), health_check, and 15 new
TypeScript client libraries for SaaS relay, auth, admin, telemetry, and kernel
sub-systems (a2a, agent, chat, hands, skills, triggers).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

desktop/src/lib/saas-errors.ts

@@ -0,0 +1,16 @@
+/**
+ * SaaS Error Class
+ *
+ * Custom error for SaaS API responses.
+ */
+
+export class SaaSApiError extends Error {
+  constructor(
+    public readonly status: number,
+    public readonly code: string,
+    message: string,
+  ) {
+    super(message);
+    this.name = 'SaaSApiError';
+  }
+}