v2.0.0 — first-class PHP SDK

Ground-up PHP SDK: PHP 8.1+, zero runtime dependencies (ext-curl/ext-json only — works on shared hosting and inside WordPress), typed exceptions, retry with backoff honoring Retry-After, keyless demo mode, raw() escape hatch for any endpoint. 16 tests / 80 assertions, CI on PHP 8.1/8.2/8.3. Packagist listing pending.