fix(golang): mark GlobalVar dependencies as IsInvoked when directly c…

[wzekin]

What type of PR is this?

fix

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• This PR title match the format: <type>(optional scope): <description>
• The description of this PR title is user-oriented and clear enough for others to understand.
• Attach the PR updating the user documentation if the current PR requires user awareness at the usage level. User docs repo

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在 golang parser 中，当一个包级变量持有函数值（如 var Foo = func() {...}），并在另一个函数体内通过 Foo() 直接调用时，abcoder 之前只会把 Foo 记为普通的 GlobalVar 依赖。函数/方法调用依赖已经通过
directCalls 匹配获得了 Extra["IsInvoked"]=true 标记，但同样的逻辑没有应用到 GlobalVars 上。下游消费者因此无法区分"引用一个全局变量"和"把全局变量作为可调用对象调用"。

Example

Input source (pkg/util.go):

package pkg

var Var6 = func() {}

// 仅引用，不调用
func Case_Func_Global() {
    _ = Var6
}

// 直接调用
func Case_Invoke_GlobalFuncVar() {
    Var6()
}

Before this PR — 两个函数的 GlobalVars 条目完全一样，无法区分"引用"和"调用"：

"Case_Func_Global": {
  "GlobalVars": [
    { "ModPath": "a.b/c", "PkgPath": "a.b/c/pkg", "Name": "Var6",
      "File": "pkg/util.go", "Line": 121 }
  ]
},
"Case_Invoke_GlobalFuncVar": {
  "GlobalVars": [
    { "ModPath": "a.b/c", "PkgPath": "a.b/c/pkg", "Name": "Var6",
      "File": "pkg/util.go", "Line": 132 }
  ]
}

After this PR — 直接调用点会带上 Extra: { "IsInvoked": true }，纯引用点保持原样：

"Case_Func_Global": {
  "GlobalVars": [
    { "ModPath": "a.b/c", "PkgPath": "a.b/c/pkg", "Name": "Var6",
      "File": "pkg/util.go", "Line": 121 }                       // 无 Extra
  ]
},
"Case_Invoke_GlobalFuncVar": {
  "GlobalVars": [
    { "ModPath": "a.b/c", "PkgPath": "a.b/c/pkg", "Name": "Var6",
      "File": "pkg/util.go", "Line": 132,
      "Extra": { "IsInvoked": true } }                           // 新增标记
  ]
}

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(optional) The PR that updates user documentation: