Simplify workspace creation with inline worktree API

Replace the multi-step new-agent route flow with a single
create_paseo_worktree endpoint that registers the workspace immediately
and creates the git worktree in the background. The sidebar now calls
this endpoint directly and shows a creating spinner inline.

Also auto-resolves the base branch from origin/HEAD when not explicitly
provided, removes the unused Tauri WebSocket transport layer, and
normalizes loopback endpoints to localhost.

Closes #125

packages/app/src/utils/host-routes.test.ts

@@ -1,7 +1,6 @@
 import { describe, expect, it } from "vitest";
 import {
   buildHostAgentDetailRoute,
-  buildHostNewAgentRoute,
   buildHostRootRoute,
   buildHostWorkspaceAgentRoute,
   buildHostWorkspaceFileRoute,
@@ -66,16 +65,6 @@ describe("workspace route parsing", () => {
     expect(buildHostRootRoute("local")).toBe("/h/local");
   });
 
-  it("builds host new-agent routes", () => {
-    expect(buildHostNewAgentRoute("local")).toBe("/h/local/new-agent");
-    expect(
-      buildHostNewAgentRoute("local", {
-        workingDir: "/tmp/repo",
-        worktreeMode: "create",
-      })
-    ).toBe("/h/local/new-agent?workingDir=%2Ftmp%2Frepo&worktreeMode=create");
-  });
-
   it("builds workspace routes with open intent query", () => {
     expect(buildHostWorkspaceAgentRoute("local", "/tmp/repo", "agent-1")).toBe(
       "/h/local/workspace/L3RtcC9yZXBv?open=agent%3Aagent-1"