fix(maestro): spawn similar preselects the cloned project

Spawn similar dropped the session's cwd into the free-text directory hatch,
so the project picker showed nothing selected. For a worktree session that
cwd was the daemon-made checkout, and the worktree toggle defaulted on, so
the clone asked for a worktree of a worktree.

It now seeds the picker: the cloned project's box selected, the same
worktree decision, base repo plus '+ new' when the source had a worktree.
A seeded path that matches no project falls back to the raw input showing
that path instead of an empty picker.

web/src/spawnSimilar.test.ts

@@ -0,0 +1,45 @@
+import { describe, expect, it } from "vitest";
+import { spawnSimilarSeed } from "./spawnSimilar.js";
+import type { Session } from "./types.js";
+
+function session(overrides: Partial<Session> = {}): Session {
+  return {
+    id: "s1",
+    cwd: "/repos/app",
+    command: "claude",
+    env: {},
+    metadata: {},
+    status: "Running",
+    created_at: "2026-01-01T00:00:00Z",
+    ...overrides,
+  } as Session;
+}
+
+describe("spawnSimilarSeed (#28)", () => {
+  it("seeds the project picker, not the free-text hatch", () => {
+    const seed = spawnSimilarSeed(session());
+    expect(seed.cwd).toBe("/repos/app");
+    expect(seed.command).toBe("claude");
+    expect(seed.cwdRawVisible).toBe(false);
+  });
+
+  it("keeps the worktree toggle off for a session that has no worktree", () => {
+    expect(spawnSimilarSeed(session()).worktreeEnabled).toBe(false);
+  });
+
+  it("clones a worktree session as a new worktree of its base repo", () => {
+    const seed = spawnSimilarSeed(
+      session({
+        cwd: "/repos/app-worktrees/feature",
+        worktree: { path: "/repos/app-worktrees/feature", base_repo: "/repos/app" },
+      }),
+    );
+    expect(seed.cwd).toBe("/repos/app");
+    expect(seed.worktreeEnabled).toBe(true);
+  });
+
+  it("never carries the cloned session's name", () => {
+    const seed = spawnSimilarSeed(session({ metadata: { name: "amber-falcon" } }));
+    expect(seed.name).toBeUndefined();
+  });
+});