docs(plugin-arch): 归档插件架构迁移评估 + plan 第11节整改计划

- docs/zh/架构迁移评估.md: C ABI→子进程+共享内存完整迁移论证(1621行)
- docs/zh/experiments/: 18项可复跑可行性实验(架构评估的所有数字来源)
- plan.md §11: 11.1~11.9 插件架构缺陷修复清单(唯一权威编号)
- main 保持干净,本批次为 update 特性分支的整改起点

docs/zh/experiments/plugin-arch/02-feasibility/exp8_worker.go

@@ -0,0 +1,50 @@
+//go:build ignore
+package main
+
+import (
+	"bufio"
+	"encoding/binary"
+	"encoding/json"
+	"fmt"
+	"os"
+	"strconv"
+
+	"golang.org/x/sys/unix"
+)
+
+// 模拟插件：拿锁 → 读 final_text → 追加自己的标记 → 写回 → 放锁
+// 锁通过 stdio RPC 向内核申请（方案 3.7：锁仲裁回归内核，无 cgo）
+func main() {
+	tag := os.Args[1]
+	shmf := os.NewFile(3, "shm")
+	data, err := unix.Mmap(int(shmf.Fd()), 0, 65536, unix.PROT_READ|unix.PROT_WRITE, unix.MAP_SHARED)
+	if err != nil { fmt.Fprintln(os.Stderr, "mmap:", err); os.Exit(1) }
+
+	dec := json.NewDecoder(bufio.NewReader(os.Stdin))
+	w := bufio.NewWriter(os.Stdout)
+	enc := json.NewEncoder(w)
+	rpc := func(method string) {
+		enc.Encode(map[string]string{"method": method}); w.Flush()
+		var r map[string]interface{}; dec.Decode(&r)
+	}
+
+	const iters = 300
+	for i := 0; i < iters; i++ {
+		rpc("stage.lock")
+		// --- 临界区：偏移解引用读写 final_text ---
+		off := binary.LittleEndian.Uint32(data[0:4])
+		ln := binary.LittleEndian.Uint32(data[4:8])
+		cur := string(data[off : off+ln])
+		add := tag
+		newS := cur + add
+		// append-only arena：写到新位置
+		newOff := binary.LittleEndian.Uint32(data[8:12])
+		if int(newOff)+len(newS) > 65536 { rpc("stage.unlock"); break }
+		copy(data[newOff:], []byte(newS))
+		binary.LittleEndian.PutUint32(data[0:4], newOff)
+		binary.LittleEndian.PutUint32(data[4:8], uint32(len(newS)))
+		binary.LittleEndian.PutUint32(data[8:12], newOff+uint32(len(newS)))
+		rpc("stage.unlock")
+	}
+	fmt.Fprintln(os.Stderr, "worker "+tag+" done, iters="+strconv.Itoa(iters))
+}