Rename the unicode files to match UnicodeTranscoder (#25)

Follow-up to the class rename, keeping the one-file-per-class naming the
rest of src/ uses (string_utilities.cc holds StringUtilities).

- src/internal/unicode.h      -> src/internal/unicode_transcoder.h
- src/unicode.cc              -> src/unicode_transcoder.cc
- tests/unicode_test.cc       -> tests/unicode_transcoder_test.cc

The three includes and one comment reference follow. Both CMakeLists
collect sources by glob, so neither needed an edit.

The gtest suite names are deliberately left alone: UnicodeCoreTest
exercises the transcoder directly, but UnicodeTest goes through
StringUtilities::ToUtf8/FromUtf8, so naming it after the class would
describe the wrong unit.

Verified locally on Linux GCC at C++11 and C++20, both configured from
scratch so the globs were re-evaluated: 124/124 tests pass in both,
clang-format clean on the changed files.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YLXHcZjrnrdhRZAgqDh6kd

Author: claude

src/internal/unicode.h src/internal/unicode_transcoder.hsrc/internal/unicode.h renamed to src/internal/unicode_transcoder.h

@@ -24,7 +24,7 @@
 
 #include <numeric>
 
-#include "internal/unicode.h"
+#include "internal/unicode_transcoder.h"
 
 using namespace sqlite_reflection;
 
@@ -46,7 +46,7 @@ To cast_each(const From& source) {
 // wchar_t holds UTF-16 code units where it is 16 bits wide (Windows) and Unicode code points
 // where it is 32 bits wide (Linux, macOS). Selecting the path by width is what keeps text above
 // U+FFFF identical across platforms; a single facet cannot serve both, which is the defect this
-// replaced. See internal/unicode.h.
+// replaced. See internal/unicode_transcoder.h.
 template <size_t WideCharSize>
 struct WideCodec;
 

src/string_utilities.cc

@@ -20,7 +20,7 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-#include "internal/unicode.h"
+#include "internal/unicode_transcoder.h"
 
 #include <stdexcept>
 

src/unicode.cc src/unicode_transcoder.ccsrc/unicode.cc renamed to src/unicode_transcoder.cc

@@ -20,7 +20,7 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-#include "internal/unicode.h"
+#include "internal/unicode_transcoder.h"
 
 #include <gtest/gtest.h>