feat(agent): ship the Go agent canvas port — eino interrupt/resume + Redis check-pointing (#16035)

Replaces the Python agent canvas runtime with a Go implementation that
runs inside `cmd/server_main`.

The canvas compiles into an eino Workflow that pauses on wait-for-user
via native Interrupt/Resume (no sentinel flag) and resumes from a
Redis-backed CheckPointStore.

All 21 Python agent components and ~35 tools are ported with functional
parity.

Sandbox providers now read their JSON config from the admin-panel
system_settings table with env fallback.

234 files / +35,413 / -6,111. All Go files are gofmt-clean (CI gate
added); drops the v2 DSL E2E step and the gap-analysis plan (both
redundant after the port ships).

## Type of change

- [x] Refactoring
- [x] New feature
- [x] Bug fix

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude <noreply@anthropic.com>

test/testcases/restful_api/test_agents.py

@@ -139,8 +139,11 @@ def test_agents_crud_validation_contract(rest_client, create_agent_resource):
     invalid_delete = rest_client.delete("/agents/invalid-agent-id")
     assert invalid_delete.status_code == 200
     invalid_delete_payload = invalid_delete.json()
+    # code=103 = permission denied (Python: "Only the owner of the agent..."; Go: "Make sure you have permission...")
     assert invalid_delete_payload["code"] == 103, invalid_delete_payload
-    assert "Only the owner of the agent is authorized for this operation." in invalid_delete_payload["message"], invalid_delete_payload
+    msg = invalid_delete_payload["message"]
+    assert ("Only the owner of the agent is authorized" in msg
+            or "Make sure you have permission" in msg), invalid_delete_payload
 
     delete_res = rest_client.delete(f"/agents/{agent_id}")
     assert delete_res.status_code == 200

test/testcases/restful_api/test_agents_go_mode.py

@@ -0,0 +1,62 @@
+import os
+import uuid
+import pytest
+
+pytestmark = pytest.mark.skipif(
+    os.environ.get("API_PROXY_SCHEME", "python") != "go",
+    reason="Go mode only (set API_PROXY_SCHEME=go + bin/ragflow_server on 9384)",
+)
+
+V2_DSL = {
+    "graph": {
+        "nodes": [
+            {"id": "begin", "type": "beginNode", "position": {"x": 50, "y": 200},
+             "data": {"label": "Begin", "name": "begin"}},
+            {"id": "answer:0", "type": "messageNode", "position": {"x": 400, "y": 200},
+             "data": {"label": "Answer", "name": "answer"}},
+        ],
+        "edges": [
+            {"id": "xy-edge__begin-answer:0", "source": "begin", "target": "answer:0",
+             "sourceHandle": "end", "targetHandle": "start"},
+        ],
+    },
+    "components": {
+        "begin":    {"obj": {"component_name": "Begin",  "params": {}}, "downstream": ["answer:0"], "upstream": []},
+        "answer:0": {"obj": {"component_name": "Answer", "params": {}}, "downstream": [],          "upstream": ["begin"]},
+    },
+    "retrieval": [], "history": [], "path": [], "variables": [], "globals": {"sys.query": ""},
+}
+
+
+@pytest.mark.p2
+def test_v2_dsl_round_trip_position_preserved(rest_client):
+    # Unique title per run so the test is idempotent (Go returns 102 on duplicate).
+    title = f"go_v2_e2e_{uuid.uuid4().hex[:8]}"
+
+    # 1. POST v2 DSL
+    r = rest_client.post("/agents", json={"title": title, "dsl": V2_DSL})
+    assert r.status_code == 200 and r.json()["code"] == 0, r.text
+    agent_id = r.json()["data"]["id"]
+
+    # 2. GET — verify v2 shape (graph + components, NO _layout)
+    dsl = rest_client.get(f"/agents/{agent_id}").json()["data"]["dsl"]
+    assert "graph" in dsl, f"v2 must have 'graph', got keys={sorted(dsl.keys())}"
+    assert "_layout" not in dsl, f"v2 must NOT emit '_layout', got keys={sorted(dsl.keys())}"
+    assert "components" in dsl
+    assert len(dsl["graph"]["nodes"]) == 2
+    assert len(dsl["graph"]["edges"]) == 1
+
+    # 3. PUT — move begin node to (777, 888)
+    new_dsl = {**V2_DSL, "graph": {**V2_DSL["graph"]}}
+    new_dsl["graph"]["nodes"] = [
+        {**n, "position": {"x": 777, "y": 888}} if n["id"] == "begin" else n
+        for n in V2_DSL["graph"]["nodes"]
+    ]
+    r = rest_client.put(f"/agents/{agent_id}", json={"title": title, "dsl": new_dsl})
+    assert r.status_code == 200 and r.json()["code"] == 0, r.text
+
+    # 4. Re-GET — position preserved
+    pos = next(n["position"] for n in
+               rest_client.get(f"/agents/{agent_id}").json()["data"]["dsl"]["graph"]["nodes"]
+               if n["id"] == "begin")
+    assert pos == {"x": 777, "y": 888}, f"position lost: {pos}"