feat: 实现loadFunction预加载函数能力 + AI辅助编程标识

- 新增 loadFunction/callFunction/unloadFunction 预加载函数 API
- 预加载语义：加载文件→顶层执行一次→返回函数存入Lua Registry→可多次调用
- 与管道模式(load/runScript)存储完全解耦：funcs[]+Registry vs pkgs[]+虚拟栈
- 新增错误码 5023/5024/5025
- 新增单元测试：仓颉侧 8 个 + C++ GTest 侧 11 个
- 本机以 Cangjie 1.1.0 实编译并通过功能运行验证
- README/doc 增加 AI 辅助编程标识及预加载函数模式说明

src/lua_runner_test.cj

@@ -323,3 +323,178 @@ func testDefaultIOCallback(): Unit {
     let result = unsafe { defaultIO() }
     @Expect(result, 0)
 }
+
+// ====================
+// 8. loadFunction / callFunction 预加载测试
+// ====================
+
+@Test
+func testLoadFunctionAndCall(): Unit {
+    let runner = LuaRunner()
+    runner.loadFunction(scriptPath("func_add.lua"), "add")
+    let res = runner.callFunction("add", "hello")
+    // 闭包带计数器，第一次调用应返回 call #1
+    @Expect(res, "result: hello (call #1)")
+}
+
+@Test
+func testCallFunctionMultipleTimes(): Unit {
+    let runner = LuaRunner()
+    runner.loadFunction(scriptPath("func_multi_call.lua"), "multi")
+
+    let r1 = runner.callFunction("multi", "")
+    @Expect(r1, "multi:init-done")
+
+    let r2 = runner.callFunction("multi", "")
+    @Expect(r2, "multi:init-done")
+
+    let r3 = runner.callFunction("multi", "")
+    @Expect(r3, "multi:init-done")
+
+    let r4 = runner.callFunction("multi", "")
+    @Expect(r4, "multi:init-done")
+}
+
+@Test
+func testCallFunctionCallCount(): Unit {
+    let runner = LuaRunner()
+    runner.loadFunction(scriptPath("func_add.lua"), "add")
+
+    @Expect(runner.callFunction("add", "a"), "result: a (call #1)")
+    @Expect(runner.callFunction("add", "b"), "result: b (call #2)")
+    @Expect(runner.callFunction("add", "c"), "result: c (call #3)")
+}
+
+@Test
+func testCallFunctionNotFound(): Unit {
+    let runner = LuaRunner()
+    try {
+        runner.callFunction("nonexistent", "")
+        fail("Should throw function not found error")
+    } catch (e: LuaError) {
+        @Expect(e.code, 5023)
+    }
+}
+
+@Test
+func testLoadFunctionFileNotFound(): Unit {
+    let runner = LuaRunner()
+    try {
+        runner.loadFunction("/no/such/file.lua", "bad")
+        fail("Should throw file not found error")
+    } catch (e: LuaError) {
+        @Expect(e.code, 5003)
+    }
+}
+
+@Test
+func testLoadFunctionNotAFunction(): Unit {
+    let runner = LuaRunner()
+    try {
+        runner.loadFunction(scriptPath("func_not_a_function.lua"), "bad")
+        fail("Should throw function not valid error")
+    } catch (e: LuaError) {
+        @Expect(e.code, 5025)
+    }
+}
+
+@Test
+func testLoadFunctionDuplicate(): Unit {
+    let runner = LuaRunner()
+    runner.loadFunction(scriptPath("func_add.lua"), "dup")
+    try {
+        runner.loadFunction(scriptPath("func_add.lua"), "dup")
+        fail("Should throw on duplicate name")
+    } catch (e: LuaError) {
+        @Expect(e.code, 5023)
+    }
+}
+
+@Test
+func testCallFunctionRuntimeError(): Unit {
+    let runner = LuaRunner()
+    runner.loadFunction(scriptPath("func_runtime_error.lua"), "bad")
+    try {
+        runner.callFunction("bad", "")
+        fail("Should throw runtime error")
+    } catch (e: LuaError) {
+        @Expect(e.code, 5010)
+    }
+}
+
+@Test
+func testCallFunctionWithUnloadFunction(): Unit {
+    let runner = LuaRunner()
+    runner.loadFunction(scriptPath("func_add.lua"), "add")
+    @Expect(runner.callFunction("add", "before"), "result: before (call #1)")
+
+    runner.unloadFunction("add")
+
+    try {
+        runner.callFunction("add", "")
+        fail("Should throw function not found after unloadFunction")
+    } catch (e: LuaError) {
+        @Expect(e.code, 5023)
+    }
+
+    // 卸载后可重新加载同名函数
+    runner.loadFunction(scriptPath("func_add.lua"), "add")
+    @Expect(runner.callFunction("add", "after"), "result: after (call #1)")
+}
+
+@Test
+func testLoadFunctionAndPipelineNoInterference(): Unit {
+    let runner = LuaRunner()
+    // 预加载函数（用独立 func 脚本）
+    runner.loadFunction(scriptPath("func_add.lua"), "add")
+    @Expect(runner.callFunction("add", "x"), "result: x (call #1)")
+
+    // 管道模式（用 pipeline 脚本，走 pkgs 栈）
+    runner.load(scriptPath("pipeline_add_suffix.lua"), "add_suffix")
+        .load(scriptPath("pipeline_to_upper.lua"), "to_upper")
+        .load(scriptPath("pipeline_add_prefix.lua"), "add_prefix")
+
+    let initialData = runner.runScript(scriptPath("pipeline_generate_data.lua"), "hello")
+    @Expect(initialData, "hello")
+
+    @Expect(runner.runScript("", ""), "[PREFIX] hello")
+    @Expect(runner.runScript("", ""), "[PREFIX] HELLO")
+    @Expect(runner.runScript("", ""), "[PREFIX] HELLO [SUFFIX]")
+
+    // 管道结束后，预加载函数仍可调用，且计数器继续
+    @Expect(runner.callFunction("add", "y"), "result: y (call #2)")
+}
+
+@Test
+func testLoadFunctionAndCleanCoexists(): Unit {
+    let runner = LuaRunner()
+    runner.loadFunction(scriptPath("func_add.lua"), "add")
+    @Expect(runner.callFunction("add", "x"), "result: x (call #1)")
+
+    runner.clear()
+
+    try {
+        runner.callFunction("add", "")
+        fail("Should throw after clean")
+    } catch (e: LuaError) {
+        @Expect(e.code, 5023)
+    }
+}
+
+@Test
+func testLoadFunctionOverflow(): Unit {
+    ensureGeneratedScriptsDir()
+    let runner = LuaRunner()
+
+    for (i in 0..20) {
+        let name = "overflow_func_${i}"
+        let path = generatedScriptPath(name + ".lua")
+        File.writeTo(path, ("return function() return \"" + name + "\" end").toArray())
+        try {
+            runner.loadFunction(path, name)
+        } catch (e: LuaError) {
+            @Expect(e.code, 5024)
+            break
+        }
+    }
+}