Add seeded task workspace creation

Current persistent tasks started with an empty workspace, which blocked the first useful host-to-task workflow in the task roadmap. This change lets task creation start from a host directory or tar archive without changing the one-shot VM surfaces.

Expose source_path on task create across the CLI, SDK, and MCP, add safe archive upload and extraction support for guest and host-compat backends, persist workspace_seed metadata, and patch the per-task rootfs with the bundled guest agent before boot so seeded guest tasks work without republishing environments. Also switch post--- command reconstruction to shlex.join() so documented sh -lc task examples preserve argument boundaries.

Validation:
- uv lock
- UV_CACHE_DIR=.uv-cache uv run pytest --no-cov tests/test_vm_guest.py tests/test_vm_manager.py tests/test_cli.py tests/test_api.py tests/test_server.py tests/test_public_contract.py
- UV_CACHE_DIR=.uv-cache make check
- UV_CACHE_DIR=.uv-cache make dist-check
- real guest-backed smoke: task create --source-path, task exec -- cat note.txt, task delete

tests/test_api.py

@@ -114,14 +114,23 @@ def test_pyro_task_methods_delegate_to_manager(tmp_path: Path) -> None:
         )
     )
 
-    created = pyro.create_task(environment="debian:12-base", allow_host_compat=True)
+    source_dir = tmp_path / "seed"
+    source_dir.mkdir()
+    (source_dir / "note.txt").write_text("ok\n", encoding="utf-8")
+
+    created = pyro.create_task(
+        environment="debian:12-base",
+        allow_host_compat=True,
+        source_path=source_dir,
+    )
     task_id = str(created["task_id"])
-    executed = pyro.exec_task(task_id, command="printf 'ok\\n'")
+    executed = pyro.exec_task(task_id, command="cat note.txt")
     status = pyro.status_task(task_id)
     logs = pyro.logs_task(task_id)
     deleted = pyro.delete_task(task_id)
 
     assert executed["stdout"] == "ok\n"
+    assert created["workspace_seed"]["mode"] == "directory"
     assert status["command_count"] == 1
     assert logs["count"] == 1
     assert deleted["deleted"] is True