fix(test): lcov reporter now counts only executable lines (#23320)

Fixes #12095

Manually confirmed to fix the case, but it would be better to have an
automated test to compare default reporter output with lcov reporter
output.

---------

Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: pfg <pfg@pfg.pw>

src/sourcemap/CodeCoverage.zig

@@ -252,7 +252,7 @@ pub const Report = struct {
             }
 
             // LF: lines found
-            try writer.print("LF:{d}\n", .{report.total_lines});
+            try writer.print("LF:{d}\n", .{report.executable_lines.count()});
 
             // LH: lines hit
             try writer.print("LH:{d}\n", .{report.lines_which_have_executed.count()});