fix: switch FastAPI routes to Pydantic body models for MCP tools/call

The plan's route signatures used query parameters, which worked for direct
HTTP callers and unit tests, but fastapi-mcp's HTTP transport passes
tools/call arguments as a JSON body. dict-typed parameters like
spark_conf arrived as a string and the route returned 422.

Refactor each route to take a single Pydantic body model (saved in
spark_executor/tools/requests.py). Underlying tool functions unchanged.

Integration tests in tests/integration/test_mcp_routes.py now exercise
the full body-based roundtrip (save_connection with spark_conf, prepare
→ list → get, list_connections with empty body).

tests/integration/test_mcp_routes.py

@@ -1,7 +1,28 @@
 # coding=utf-8
+from pathlib import Path
+
+import pytest
 from fastapi.testclient import TestClient
 
+from spark_executor.core import connection_store, pending_store
+from spark_executor.core.connection_store import ConnectionStore
+from spark_executor.core.pending_store import PendingStore
 from spark_executor.server import app
+from spark_executor.tools import connections, submit
+
+
+@pytest.fixture(autouse=True)
+def _fresh_data(tmp_path: Path, monkeypatch):
+    """Reset both stores to a fresh tmp dir and rebind the singletons that
+    the tool modules captured at import time."""
+    monkeypatch.setattr(connection_store, "DEFAULT_DATA_DIR", str(tmp_path))
+    monkeypatch.setattr(connection_store, "store", ConnectionStore())
+    monkeypatch.setattr(pending_store, "DEFAULT_DATA_DIR", str(tmp_path))
+    monkeypatch.setattr(pending_store, "store", PendingStore())
+    # Rebind imports inside the tool modules (captured at import time)
+    connections.store = connection_store.store
+    submit.conn_store = connection_store.store
+    submit.pending_store = pending_store.store
 
 
 def test_health_still_present():
@@ -31,3 +52,61 @@ def test_twelve_tool_routes_registered():
         "/delete_connection",
     ):
         assert path in paths, f"missing MCP tool route: {path}"
+
+
+# --- End-to-end body-based calls (the gap the route-registration test missed) ---
+
+def test_save_connection_accepts_dict_spark_conf_in_body():
+    """The original query-param signature returned 422 for spark_conf dicts;
+    body models make tools/call roundtrip cleanly."""
+    c = TestClient(app)
+    r = c.post(
+        "/save_connection",
+        json={
+            "name": "prod",
+            "master": "yarn",
+            "deploy_mode": "cluster",
+            "spark_conf": {"spark.sql.shuffle.partitions": "200"},
+        },
+    )
+    assert r.status_code == 200, r.text
+    assert r.json() == {"name": "prod", "status": "SAVED"}
+
+
+def test_prepare_submit_job_works_via_body():
+    c = TestClient(app)
+    c.post("/save_connection", json={"name": "prod", "master": "yarn"})
+    r = c.post(
+        "/prepare_submit_job",
+        json={"connection": "prod", "script_path": "/tmp/demo.py", "queue": "research"},
+    )
+    assert r.status_code == 200, r.text
+    body = r.json()
+    assert body["status"] == "PENDING"
+    assert body["pending_id"].startswith("p_")
+    assert body["parameters"]["queue"] == "research"
+    assert body["parameters"]["master"] == "yarn"  # snapshotted from connection
+
+
+def test_list_and_get_pending_job_roundtrip_via_body():
+    c = TestClient(app)
+    c.post("/save_connection", json={"name": "prod", "master": "yarn"})
+    prep = c.post(
+        "/prepare_submit_job",
+        json={"connection": "prod", "script_path": "/tmp/a.py"},
+    ).json()
+    pid = prep["pending_id"]
+
+    listed = c.post("/list_pending_jobs", json={}).json()
+    assert any(p["pending_id"] == pid for p in listed)
+
+    got = c.post("/get_pending_job", json={"pending_id": pid}).json()
+    assert got["script_path"] == "/tmp/a.py"
+    assert got["status"] == "PENDING"
+
+
+def test_list_connections_works_with_empty_body():
+    c = TestClient(app)
+    r = c.post("/list_connections", json={})
+    assert r.status_code == 200
+    assert r.json() == []