docs(book): Update README with Chapter 11 completion stats

- Chapter 11: 5,720 → 13,831 words (+8,111 words, +142% expansion)
- Part II subtotal: 12,031 → 20,142 words
- Total content: ~104,000 → ~112,000 words
- Updated topics: added Kalman filter, risk management, Aug 2007

Author: 0xrinegade

docs/book/README.md

@@ -10,7 +10,7 @@ This textbook provides comprehensive coverage of algorithmic trading strategies,
 
 **Level:** Graduate (MFE, MQF, MS in Computational Finance)
 **Prerequisites:** Calculus, probability theory, basic programming
-**Total Content:** ~104,000 words across 16 chapters (13 original + 3 NEW foundational chapters)
+**Total Content:** ~112,000 words across 16 chapters (13 original + 3 NEW foundational chapters)
 **Academic References:** 156 peer-reviewed papers and textbooks (134 original + 22 NEW)
 
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@@ -62,10 +62,10 @@ Every chapter shows you **exactly** how these disasters could have been prevente
 
 | Chapter | Title | Words | Topics |
 |---------|-------|-------|--------|
-| [11](11_pairs_trading.md) | Statistical Arbitrage — Pairs Trading | 5,720 | Cointegration, O-U process, 2007 quant quake |
+| [11](11_pairs_trading.md) | Statistical Arbitrage — Pairs Trading | 13,831 | Cointegration, O-U process, Kalman filter, risk mgmt, Aug 2007 |
 | [12](12_options_volatility.md) | Options Pricing and Volatility Surface | 6,311 | Black-Scholes, Greeks, vol smile/skew |
 
-**Subtotal:** 12,031 words
+**Subtotal:** 20,142 words
 
 ### Part III: Machine Learning & AI