Malformed JSON output due to erroneous UTF-8 character splitting

[maximal]

This code breaks JSON formatter entirely (and the overall output slightly):

<?php

$message = sprintf(
	// Note the erroneous `ы` instead of `s` -----------------↓
	"[%s][Some string with erroneous unicode specifier] %s = %ы",
	(new \DateTimeImmutable())->format("d.m.Y H:i:s.v"),
	'topic',
	'message'
);

echo $message, PHP_EOL;

JSON formatter exception:

$ ./vendor/bin/psalm --output-format=json

Target PHP version: 8.3 (inferred from composer.json).
Scanning files...
Analyzing files...

E
Uncaught RuntimeException: Cannot create JSON string: Malformed UTF-8 characters, possibly incorrectly encoded in /path/to/project/vendor/vimeo/psalm/src/Psalm/Internal/Json/Json.php:41
Stack trace:
#0 /path/to/project/vendor/vimeo/psalm/src/Psalm/Report/JsonReport.php(27): Psalm\Internal\Json\Json::encode(Array, 0)
#1 /path/to/project/vendor/vimeo/psalm/src/Psalm/IssueBuffer.php(945): Psalm\Report\JsonReport->create()
#2 /path/to/project/vendor/vimeo/psalm/src/Psalm/IssueBuffer.php(653): Psalm\IssueBuffer::getOutput(Array, Object(Psalm\Report\ReportOptions), Array)
#3 /path/to/project/vendor/vimeo/psalm/src/Psalm/Internal/Cli/Psalm.php(399): Psalm\IssueBuffer::finish(Object(Psalm\Internal\Analyzer\ProjectAnalyzer), true, 1723569466.044, false, Array)
#4 /path/to/project/vendor/vimeo/psalm/psalm(9): Psalm\Internal\Cli\Psalm::run(Array)
#5 /path/to/project/vendor/bin/psalm(119): include('/path/to/projec...')
#6 {main}
(Psalm 5.25.0@01a8eb06b9e9cc6cfb6a320bf9fb14331919d505 crashed due to an uncaught Throwable)

GitHub formatter works without exceptions, although Psalm erroneously calculates the character (cuts two bytes of UTF-8 encoded ы in half getting �):

$ ./vendor/bin/psalm --output-format=github

Target PHP version: 8.3 (inferred from composer.json).
Scanning files...
Analyzing files...


::error file=test.php,line=3,col=12,title=InvalidArgument::test.php:3:12: InvalidArgument: Argument 1 of sprintf is invalid - Unknown format specifier "�" (see https://psalm.dev/004)
------------------------------
1 errors found
------------------------------

Checks took 0.01 seconds and used 1.692MB of memory
No files analyzed
Psalm was able to infer types for 100% of the codebase

The web service at https://psalm.dev/ gives empty response for this code, because it cannot build the JSON output for it.

[weirdan]

although Psalm erroneously calculates the character (cuts two bytes of UTF-8 encoded ы in half getting �):

Actually, that's kinda correct. sprintf() takes one byte after the % character (if we ignore width specification for the sake of simplicity) as a specifier.

Now of course this shouldn't break output formatters.