docs: add complete PHP SDK wiki documentation
Create full wiki matching the JavaScript SDK wiki structure and style,
adapted for PHP's request-scoped execution model and PSR standards.
17 files covering:
- Home page with architecture diagram and JS SDK differences
- 11 chapters: Core, Context, ExperienceManager, FeatureManager,
DataManager, BucketingManager, RuleManager, ApiManager, EventManager,
SegmentsManager, Config/Types
- User Guide with full API reference
- Data Model Reference with entity relationships
- AI Index, Sidebar, and Footer navigation
Key PHP-specific adaptations documented:
- Synchronous ConvertSDK::create() static factory
- PSR-3/16/18 integration (logging, caching, HTTP)
- PSR-16 cache as dual-purpose config + visitor data store
- No timeouts/timers — register_shutdown_function for queue flush
- Simplified DataStoreManager (clean passthrough, no queue)
- Readonly DTOs and backed PHP enums
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>