feat(agent): align Go agent behavior with Python (except retrieval component) (#16225)

## Summary

Aligns the **Go agent runtime/canvas/components/tools** behavior with
the **Python `agent/` implementation** so the same stored canvas DSL
produces the same execution result on either side. Every component,
tool, and runtime primitive in `internal/agent/` is now driven by the
same semantics as its Python counterpart — variable resolution, template
substitution, control flow, error reporting, retry/cancel, and stream
event shapes.

The **retrieval component is the one explicit exception** in this PR. It
is being reworked in a separate change and is excluded from this
alignment pass; the wrapper slot (`universe_a_wrappers.go →
newRetrievalComponent`) is preserved.

## Scope of alignment

### Components (all aligned with `agent/component/`)
`Begin` · `Message` · `LLM` (incl. ChatTemplateKwargs,
MessageHistoryWindowSize, VisualFiles, Cite, OutputStructure,
JSONOutput, TopP, MaxRetries, DelayAfterError, credentials) · `Agent`
(react + tool artifact capture + `Reset()` interface-assert) · `Switch`
(12/12 operators, Python-equivalent semantics) · `Categorize` · `Invoke`
· `Iteration` · `Loop` (macro-expansion through `workflowx.AddLoopNode`)
· `UserFillUp` (Python-equivalent interrupt/resume via eino
`compose.Interrupt`/`ResumeWithData`) · `FillUp` · `DataOperations` ·
`ListOperations` · `StringTransform` · `VariableAggregator` ·
`VariableAssigner` · `Browser` (full stagehand runtime parity) ·
`DocsGenerator` · `ExcelProcessor`.

### Tools (all aligned with `agent/tools/`)
`Retrieval` (wrapper slot only — logic out of scope) · `MCPToolAdapter`
(streamable-HTTP) · `CodeExec` (sandbox bridge with
`code_exec_contract.go` matching Python contract) · `AkShare` · `ArXiv`
· `Crawler` · `DeepL` · `DuckDuckGo` · `Email` · `ExeSQL` · `GitHub` ·
`Google` · `GoogleScholar` · `Jin10` · `PubMed` · `QWeather` · `SearXNG`
· `Tavily` · `Tushare` · `Wencai` · `Wikipedia` · `YahooFinance` —
uniform `eino tool.InvokableTool` interface, SSRF protection, shared
HTTP client.

### Canvas execution engine (`internal/agent/canvas/`)
Aligned with Python's `agent/canvas.py`:
- **Scheduler** (`scheduler.go`): state pre/post handlers, node lambdas,
per-component timeout resolver (4-level: per-class env → per-class table
→ uniform env → 600s fallback), `legacyNoOpNames`.
- **Loop subgraph** (`loop_subgraph.go`): Python-equivalent
`AddLoopNode` macro expansion + condition translation.
- **Multibranch** (`multibranch.go`): `Switch` / `Categorize` routing
via `compose.NewGraphMultiBranch` — same branch selection semantics as
Python.
- **Parallel subgraph** (`parallel_subgraph.go`): matches Python's
parallel fan-out contract.
- **Interrupt/Resume** (`interrupt_resume.go`): `UserFillUpNodeBody` /
`IsInterruptError` / `ExtractInterruptContexts` — replaces the
deprecated Python sentinel chain with eino's native interrupt API,
preserving the same external behavior.
- **Checkpoint** (`checkpoint_store.go`): `RedisCheckPointStore`
Get/Set/Delete, with business metadata (status / canvas_id /
parent_run_id) on a parallel Redis Hash.
- **RunTracker** (`run_tracker.go`): Start / MarkSucceeded / MarkFailed
/ MarkCancelled / AttachCheckpoint — same lifecycle as the Python run
record.
- **Cancel** (`cancel.go`): Redis pub/sub watch.
- **Stream** (`stream.go`): SSE channel with `messages` / `waiting` /
`errors` / `done` events, same shape as Python's `agent.canvas.RunEvent`
payload.

### DSL bridge (`internal/agent/dsl/`)
- `normalize.go`: v1↔v2 collapsed into a single wire format — Python and
Go consume the same stored JSON.
- `reset.go`: per-run state reset matches Python's `Canvas.reset()`
semantics.
- Testdata mirrors Python's `agent_msg.json` / `all.json` / etc.

### Runtime (`internal/agent/runtime/`)
- `CanvasState` / `NewCanvasState` / `GetVar` / `SetVar` / `ReadVars`:
same `{{cpn_id@param}}` resolution model.
- `ResolveTemplate` (regex fast path + gonja fallback) — Python
Jinja-style semantics.
- `selector.go`, `metrics.go`, `component.go`: shared runtime contracts.

## Out of scope (intentionally)

- **`Retrieval` component logic** — wrapped only; full parity lands in a
follow-up PR.
- **Frontend** — only minor dsl-bridge / canvas UX fixes ride along.
- **CLI / admin / model registry** — orthogonal to agent behavior.

## How alignment is verified

`internal/service/agent_run_e2e_test.go` exercises the **full production
chain** against real Python-shaped DSL fixtures:
```
loadCanvasForUser → versionDAO.GetLatest → decodeCanvasFromDSL →
canvas.Compile → cc.Workflow.Invoke → answer extraction
```
using in-memory SQLite + miniredis (no Docker). Covers:
- `TestRunAgent_RealCanvas_BeginMessage` — happy path, `{{sys.query}}`
resolution
- `TestRunAgent_RealCanvas_WaitForUserResume` — two-run resume cycle
(Python-equivalent)
- `TestRunAgent_RealCanvas_CompileFails` — unknown component name →
sanitized error (Python-equivalent)
- `TestRunAgent_RealCanvas_InvokeFails` — unresolvable template ref
(Python-equivalent)
- `TestRunAgent_RunTracker_AttachCheckpoint_CallSequence` —
Start→AttachCheckpoint→MarkSucceeded lifecycle

`internal/handler/agent_test.go` — SSE streaming parity (`Content-Type:
text/event-stream`, `data: {…}\n\n`, trailing `data: [DONE]\n\n`,
OpenAI-compatible non-stream `choices`).

`internal/agent/canvas/fixture_compile_test.go` + per-component tests
pin the Python-equivalent outputs.

```
go test -count=1 -v -run 'TestRunAgent_RealCanvas|TestRunAgent_RunTracker' ./internal/service/
```

## Design reference

`docs/develop/agent-go-port-design.md` (1329 lines, last cross-checked
2026-06-17) — module layout, per-component / per-tool inventory,
corner-case catalogue, and the actionable backlog (Section 14, including
the retrieval alignment follow-up).

---------

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

internal/agent/tool/code_exec_test.go

@@ -193,8 +193,12 @@ func TestCodeExec_ResultSurfacesActualType(t *testing.T) {
 	t.Parallel()
 
 	resp := &SandboxResponse{
-		Returned:         `{"x": 1}`,
-		StructuredResult: map[string]any{"actual_type": "Object"},
+		StructuredResult: map[string]any{
+			"present": true,
+			"value": map[string]any{
+				"x": float64(1),
+			},
+		},
 	}
 	out, err := codeExecResultJSON(resp)
 	if err != nil {
@@ -207,8 +211,67 @@ func TestCodeExec_ResultSurfacesActualType(t *testing.T) {
 	if got.ActualType != "Object" {
 		t.Errorf("ActualType = %q, want Object", got.ActualType)
 	}
-	if got.Content != `{"x": 1}` {
-		t.Errorf("Content = %q, want %q", got.Content, `{"x": 1}`)
+	if got.Content != "{\n  \"x\": 1\n}" {
+		t.Errorf("Content = %q, want pretty JSON object", got.Content)
+	}
+}
+
+func TestCodeExec_ResultUsesStructuredResultValue(t *testing.T) {
+	t.Parallel()
+
+	resp := &SandboxResponse{
+		Returned: "8",
+		StructuredResult: map[string]any{
+			"present": true,
+			"value":   float64(8),
+		},
+	}
+	out, err := codeExecResultJSON(resp)
+	if err != nil {
+		t.Fatalf("codeExecResultJSON: %v", err)
+	}
+	var got map[string]any
+	if jerr := json.Unmarshal([]byte(out), &got); jerr != nil {
+		t.Fatalf("output not valid JSON: %v", jerr)
+	}
+	if got["raw_result"] != float64(8) {
+		t.Fatalf("raw_result = %#v, want 8", got["raw_result"])
+	}
+	if got["content"] != "8" {
+		t.Fatalf("content = %#v, want \"8\"", got["content"])
+	}
+	if got["actual_type"] != "Number" {
+		t.Fatalf("actual_type = %#v, want Number", got["actual_type"])
+	}
+}
+
+func TestCodeExec_ResultFallsBackToStdoutJSON(t *testing.T) {
+	t.Parallel()
+
+	resp := &SandboxResponse{
+		Stdout: `{"a":[1,2]}`,
+	}
+	out, err := codeExecResultJSON(resp)
+	if err != nil {
+		t.Fatalf("codeExecResultJSON: %v", err)
+	}
+	var got map[string]any
+	if jerr := json.Unmarshal([]byte(out), &got); jerr != nil {
+		t.Fatalf("output not valid JSON: %v", jerr)
+	}
+	raw, ok := got["raw_result"].(map[string]any)
+	if !ok {
+		t.Fatalf("raw_result type = %T, want map[string]any", got["raw_result"])
+	}
+	arr, ok := raw["a"].([]any)
+	if !ok || len(arr) != 2 || arr[0] != float64(1) || arr[1] != float64(2) {
+		t.Fatalf("raw_result[a] = %#v, want [1 2]", raw["a"])
+	}
+	if got["actual_type"] != "Object" {
+		t.Fatalf("actual_type = %#v, want Object", got["actual_type"])
+	}
+	if got["content"] != "{\n  \"a\": [\n    1,\n    2\n  ]\n}" {
+		t.Fatalf("content = %#v, want pretty JSON", got["content"])
 	}
 }