feat: AutoZero 通用 Agent 框架（从 AutoGo 五阶段拆分完成）

llm（三协议 Provider）/ session（JSONL 持久化）/ tools（Registry、围栏、
builtin、computer）/ cdp（browser）/ skills / mcp / agent（循环、两级压缩、
编排、审批门控）+ 底座 jsonl/textx/execx/diag/scratch/spill/imagecache。

产品装配代码（config 桥接、schedule 工具、memory/plan/retro/prompt）
留在 AutoGo，宿主接入方式见 MIGRATION.md。

agent/truncate_spill_test.go

@@ -0,0 +1,61 @@
+package agent
+
+import (
+	"errors"
+	"strings"
+	"testing"
+
+	"git.gopher.ink/mirrors2/AutoZero/llm"
+)
+
+// TestTruncateSpillSavesAndReferences：截断时把原文落盘并在提示里给出可读路径。
+func TestTruncateSpillSavesAndReferences(t *testing.T) {
+	long := "HEAD" + strings.Repeat("m", 50000) + "TAIL"
+	msgs := []llm.Message{{Role: llm.RoleTool, ToolCallID: "call-1", Content: long}}
+
+	var gotID, gotFull string
+	spillFn := func(callID, full string) (string, error) {
+		gotID, gotFull = callID, full
+		return "/tmp/results/call-1.txt", nil
+	}
+
+	view := truncateToolResultsSpill(msgs, 20000, spillFn)
+
+	if gotID != "call-1" {
+		t.Errorf("spillFn got callID %q, want call-1", gotID)
+	}
+	if gotFull != long {
+		t.Errorf("spillFn must receive the full original text (got %d bytes, want %d)", len(gotFull), len(long))
+	}
+	content := view[0].Content
+	if !strings.Contains(content, "/tmp/results/call-1.txt") {
+		t.Errorf("notice should reference the spilled path:\n%s", content)
+	}
+	if !strings.Contains(content, "use the read tool") {
+		t.Errorf("notice should tell the model how to retrieve it:\n%s", content)
+	}
+	if !strings.Contains(content, "[truncated") {
+		t.Errorf("notice should mention truncation:\n%s", content)
+	}
+	if len(content) > 20000 {
+		t.Errorf("truncated content too long: %d", len(content))
+	}
+	// transcript（传入的切片）不能被修改。
+	if msgs[0].Content != long {
+		t.Error("original message must not be mutated")
+	}
+}
+
+// TestTruncateSpillFailureDegrades：落盘失败时退回"重跑工具"提示，不 panic。
+func TestTruncateSpillFailureDegrades(t *testing.T) {
+	msgs := []llm.Message{{Role: llm.RoleTool, ToolCallID: "c", Content: strings.Repeat("b", 50000)}}
+	view := truncateToolResultsSpill(msgs, 20000, func(_, _ string) (string, error) {
+		return "", errors.New("disk full")
+	})
+	if strings.Contains(view[0].Content, "full output saved") {
+		t.Errorf("failed spill must not advertise a path:\n%s", view[0].Content)
+	}
+	if !strings.Contains(view[0].Content, "narrower query") {
+		t.Errorf("failed spill should fall back to the rerun hint:\n%s", view[0].Content)
+	}
+}