重构：把剩余 12 个顶层包全部迁到 internal/

继续之前的重构：把根目录残留的非数据/资源类子目录（agents、agenttool、ai、
autoreply、completion、conversation、llm、message、mqtpp、stream、
toolmanager、toolrouter）一并搬到 internal/ 下，并把全工程引用它们的
import 路径从 "meshtastic_mqtt_server/<x>" 重写为
"meshtastic_mqtt_server/internal/<x>"。

变更
- git mv 12 个顶层目录进 internal/，无函数体改动。
- 全工程 sed 把 import path 加上 internal/ 前缀，包括 main.go、
  internal/bot/bot_service.go、internal/store/bot_store.go 中对 mqtpp
  的引用，以及 ai 子系统内部 agents/agenttool/autoreply/conversation/
  llm/toolmanager/toolrouter 之间的相互引用。

验证
- go build ./... 通过；go test ./... 全部包通过。
- AI 自动回复链路（main → ai.NewService → autoreply.Service → botSender）
  保持不变，仅 import 路径调整。
- 根目录最终只剩 main.go / main_test.go / internal/ 加 go.mod / go.sum
  与数据资源目录（dist、doc、firmware、py、win、meshmap_frontend）。

Co-Authored-By: Claude <noreply@anthropic.com>

internal/agenttool/registry.go

@@ -0,0 +1,108 @@
+package agenttool
+
+import (
+	"context"
+	"fmt"
+	"sort"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/volcengine/volcengine-go-sdk/service/arkruntime/model"
+)
+
+// LoadOptions contains options for loading a tool
+type LoadOptions struct {
+	Values map[string]any
+}
+
+// Value returns a value from the load options
+func (o LoadOptions) Value(key string) any {
+	if o.Values == nil {
+		return nil
+	}
+	return o.Values[key]
+}
+
+// Frame represents an event frame emitted by a tool
+type Frame struct {
+	Type    string
+	Tool    string
+	Stage   string
+	Status  string
+	Message string
+	Data    map[string]any
+	Error   string
+	Text    string
+}
+
+// EmitFunc is a function that emits frames
+type EmitFunc func(frame any)
+
+// Runtime provides context for tool execution
+type Runtime struct {
+	Profile      any
+	CompleteText func(context.Context, string, int) (string, error)
+	Emit         EmitFunc
+	Now          time.Time
+}
+
+// LoadedTool is the interface that all tools must implement
+type LoadedTool interface {
+	Name() string
+	Enabled() bool
+	ToolDefinition(description string) *model.Tool
+	Execute(context.Context, string, Runtime) (string, error)
+	RawState() any
+}
+
+// Descriptor describes a tool that can be loaded
+type Descriptor struct {
+	Name string
+	Load func(path string, options LoadOptions) (LoadedTool, error)
+}
+
+var (
+	registryMu sync.RWMutex
+	registry   = map[string]Descriptor{}
+)
+
+// Register registers a tool descriptor
+func Register(descriptor Descriptor) {
+	name := strings.ToLower(strings.TrimSpace(descriptor.Name))
+	if name == "" {
+		panic("agenttool: tool name is empty")
+	}
+	if descriptor.Load == nil {
+		panic(fmt.Sprintf("agenttool: %s load function is nil", name))
+	}
+	descriptor.Name = name
+
+	registryMu.Lock()
+	defer registryMu.Unlock()
+	if _, ok := registry[name]; ok {
+		panic(fmt.Sprintf("agenttool: tool %s already registered", name))
+	}
+	registry[name] = descriptor
+}
+
+// Lookup finds a tool descriptor by name
+func Lookup(name string) (Descriptor, bool) {
+	registryMu.RLock()
+	defer registryMu.RUnlock()
+	descriptor, ok := registry[strings.ToLower(strings.TrimSpace(name))]
+	return descriptor, ok
+}
+
+// Names returns all registered tool names
+func Names() []string {
+	registryMu.RLock()
+	defer registryMu.RUnlock()
+
+	names := make([]string, 0, len(registry))
+	for name := range registry {
+		names = append(names, name)
+	}
+	sort.Strings(names)
+	return names
+}