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。

llm/transient_test.go

@@ -0,0 +1,47 @@
+package llm
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"testing"
+	"time"
+)
+
+// TestIsTransientStream 钉住"该重发"与"重发也没用"的分界：前者是网关/传输层的偶发
+// 坏流，后者是确定性失败——把后者卷进重试环就是白烧预算 + 把一次明确的错误拖成十分钟。
+func TestIsTransientStream(t *testing.T) {
+	cases := []struct {
+		name string
+		err  error
+		want bool
+	}{
+		{"nil", nil, false},
+		{"整轮空补全", fmt.Errorf("openai: %w", ErrEmptyCompletion), true},
+		{"流被截断", fmt.Errorf("anthropic: %w", ErrTruncatedStream), true},
+		{"流卡死到看门狗上限", &StalledError{Idle: 90 * time.Second}, true},
+		{"包过一层的卡死", fmt.Errorf("stream: %w", &StalledError{Idle: time.Minute}), true},
+		{"连接被掐", errors.New("read tcp 10.0.0.5:52314->1.2.3.4:443: connection reset by peer"), true},
+		{"连接被拒", errors.New("dial tcp 1.2.3.4:443: connect: connection refused"), true},
+		{"读超时", errors.New("read tcp: i/o timeout"), true},
+		{"裸 EOF", io.EOF, true},
+		{"网关过载", errors.New("openai: HTTP 503: upstream busy"), true},
+		{"限流", errors.New("openai: HTTP 429 Too Many Requests"), true},
+		// 以下都是"重发只会再撞一次同一堵墙"。
+		{"请求不合法", errors.New(`openai: HTTP 400: {"error":{"message":"inference request is invalid","code":"400002"}}`), false},
+		{"上游拒了这条请求", errors.New(`openai: HTTP 400: {"error":{"code":"upstream_request_rejected","message":"Bad Request","type":"invalid_request_error"}}`), false},
+		{"没权限", errors.New("openai: HTTP 401: invalid api key"), false},
+		{"余额不足", errors.New("anthropic: credit balance is too low"), false},
+		{"上下文满", errors.New("openai: model_context_window_exceeded"), false},
+		{"用户取消", context.Canceled, false},
+		{"外部 deadline", context.DeadlineExceeded, false},
+	}
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			if got := IsTransientStream(c.err); got != c.want {
+				t.Errorf("IsTransientStream(%v) = %v, want %v", c.err, got, c.want)
+			}
+		})
+	}
+}