Please address the comments from this code review:

## Overall Comments
- Logging `ScreencapMethod` (e.g., `LogInfo << "Testing" << method` and `VAR(method)`) will require an `operator<<` overload for the enum or an explicit cast to an integral type; otherwise these log calls may not compile or will produce unreadable output.
- When `screencap_method_ == MaaWin32ScreencapMethod_None`, `init_screencap()` now returns `true` and leaves `screencap_` null, changing the previous behavior (which treated missing method as error); if callers assume a valid `screencap_` after `connect()`, consider either keeping the failure semantics or explicitly documenting and guarding against the `nullptr` case.
- The `speed_test` currently measures each screencap method with a single `screencap()` call; to reduce variance (e.g., first-call initialization costs) and improve selection stability, consider running each method multiple times and ignoring obvious outliers or adding a short warm-up phase.

## Individual Comments

### Comment 1
<location path="source/MaaWin32ControlUnit/Manager/Win32ControlUnitMgr.cpp" line_range="171-172" />
<code_context>
+    }
+}
+
+std::shared_ptr<ScreencapBase> Win32ControlUnitMgr::speed_test(
+    std::unordered_map<ScreencapMethod, std::shared_ptr<ScreencapBase>>& units) const
+{
+    LogFunc;
</code_context>
<issue_to_address>
**suggestion:** Use a const reference for the `units` parameter in `speed_test` to better express intent.

Since `speed_test` doesn’t modify `units`, the parameter can be `const std::unordered_map<ScreencapMethod, std::shared_ptr<ScreencapBase>>&`. This improves const-correctness and allows calling it with const maps.

```suggestion
std::shared_ptr<ScreencapBase> Win32ControlUnitMgr::speed_test(
    const std::unordered_map<ScreencapMethod, std::shared_ptr<ScreencapBase>>& units) const
```
</issue_to_address>

### Comment 2
<location path="source/MaaWin32ControlUnit/Manager/Win32ControlUnitMgr.cpp" line_range="188-195" />
<code_context>
+        LogInfo << VAR(method) << VAR(duration);
+    };
+
+    for (auto& [method, unit] : units) {
+        LogInfo << "Testing" << method;
+        auto now = std::chrono::steady_clock::now();
+        if (!unit->screencap()) {
+            LogWarn << "failed to test" << method;
+            continue;
+        }
+        check(method, now);
+    }
+
</code_context>
<issue_to_address>
**suggestion (performance):** Consider multiple samples or a warmup for each screencap method to avoid one-off timing artifacts.

Using only one timing per method means any one-time initialization (e.g., GPU/driver setup, first capture overhead) can dominate the measurement and bias the selection toward a method that’s not actually best in steady state. To reduce this, consider adding a warmup call and/or measuring min/average over several `screencap()` calls per method.

Suggested implementation:

```cpp
    auto check = [&fastest, &cost](ScreencapMethod method, std::chrono::steady_clock::duration duration) {
        if (duration < cost) {
            fastest = method;
            cost = duration;
        }
        LogInfo << VAR(method) << VAR(duration);
    };

```

```cpp
    constexpr int warmup_runs = 1;
    constexpr int measure_runs = 5;

    for (auto& [method, unit] : units) {
        LogInfo << "Testing" << method;

        bool warmup_ok = true;
        for (int i = 0; i < warmup_runs; ++i) {
            if (!unit->screencap()) {
                LogWarn << "failed to warmup" << method;
                warmup_ok = false;
                break;
            }
        }
        if (!warmup_ok) {
            continue;
        }

        std::chrono::steady_clock::duration best_duration = std::chrono::steady_clock::duration::max();
        bool any_success = false;

        for (int i = 0; i < measure_runs; ++i) {
            auto start = std::chrono::steady_clock::now();
            if (!unit->screencap()) {
                LogWarn << "failed to test" << method;
                continue;
            }
            auto duration = duration_since(start);
            any_success = true;
            if (duration < best_duration) {
                best_duration = duration;
            }
        }

        if (!any_success) {
            continue;
        }

        check(method, best_duration);
    }

```
</issue_to_address>