feat: IGLA Streaming Engine Cycle 18 — Token-by-Token with Async Yield

- Token-by-token streaming output (character or word level)
- Callback system for real-time token delivery
- Async yield simulation between tokens
- Progress tracking with tokens/second and ETA
- Circular token buffer for efficient streaming
- Configurable chunk size and streaming modes
- Wraps FluentChatEngine (Cycle 17) for layered architecture

Benchmark Results:
- Streams completed: 20/20 (100%)
- Tokens generated: 1067 | Callback delivery: 100%
- Avg tokens/stream: 53.4
- Speed: 13,888 ops/s
- Improvement rate: 1.00 (PASSED > 0.618)
- Tests: 75/75 passing

phi^2 + 1/phi^2 = 3 = TRINITY | KOSCHEI STREAMS ENDLESSLY | CYCLE 18

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: gHashTag