keyboard_report_util: cast keys to uint8_t in the brace-init list

Apple clang 21 fails the test build with:

    tests/test_common/keyboard_report_util.hpp:38:81: error:
      non-constant-expression cannot be narrowed from type
      'qk_keycode_defines' to 'value_type' (aka 'unsigned char') in
      initializer list [-Wc++11-narrowing]
       38 |     return testing::MakeMatcher(new KeyboardReportMatcher(
              std::vector<uint8_t>({keys...})));

Callers like EXPECT_REPORT(driver, (KC_SPACE)) deduce the variadic
pack as qk_keycode_defines, and std::vector<uint8_t>{keys...} is a
brace-init list -- the one context where C++11 narrowing rules apply.
clang's -Wc++11-narrowing rejects the implicit enum -> uint8_t
conversion there; gcc was lenient, which is why Linux CI didn't catch
this.

The narrowing is purely type-based: every real call site passes
basic keycodes that fit in a byte by construction (action-layer
processing has already reduced any wider keycodes upstream of the
report builder), but the enum type itself is wider than uint8_t and
that's what the rule keys off of. Make the conversion explicit with
a static_cast in the pack expansion so the brace-init list sees a
uint8_t to begin with and the narrowing rule has nothing to fire on.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: scottlamb

tests/test_common/keyboard_report_util.hpp

@@ -35,5 +35,5 @@ class KeyboardReportMatcher : public testing::MatcherInterface<report_keyboard_t
 
 template <typename... Ts>
 inline testing::Matcher<report_keyboard_t&> KeyboardReport(Ts... keys) {
-    return testing::MakeMatcher(new KeyboardReportMatcher(std::vector<uint8_t>({keys...})));
+    return testing::MakeMatcher(new KeyboardReportMatcher({static_cast<uint8_t>(keys)...}));
 }