Tighten stream-resource docs and package hygiene

[prateekbhujel]

Summary

• add a compatibility document for supported PHP versions, platforms, install paths, and stream-resource boundaries
• add a non-interactive examples/streams.php demo for STDOUT, STDERR, and php://temp resources
• add PHPT coverage for the new stream example
• add lightweight .gitattributes source/archive hygiene without adding GitHub issue or PR templates

Validation

• php -l examples/streams.php examples/basic.php examples/doctor.php examples/prompt.php
• Composer 2.9.8 validate --strict --no-check-lock
• git diff --check
• XAMPP PHP 8.2 x86_64 build from /private/tmp with -Wall -Wextra
• make test REPORT_EXIT_STATUS=1 NO_INTERACTION=1 TEST_PHP_EXECUTABLE=/Applications/XAMPP/xamppfiles/bin/php -> 33 total, 30 passed, 3 skipped, 0 failed
• examples/streams.php and examples/doctor.php run against the built extension

Closes #47