Consolidate fragmented documentation into organized structure

[Copilot]

Documentation was scattered across 35+ root-level markdown files with overlapping content, no clear entry point, and no distinction between current vs historical information.

Changes

New Core Documentation

• README.md (14KB) - Project overview, quick start, architecture, performance metrics
• docs/HISTORY.md (18KB) - Complete timeline: 2018 single-sport origin → 2026 9-sport platform
• docs/EXPERIMENTS.md (17KB) - All model comparisons consolidated (Elo vs TrueSkill vs XGBoost vs ML alternatives)
• docs/BACKTESTING.md (18KB) - Unified validation results across all sports with lift/gain analysis
• docs/GUIDES.md (13KB) - Navigation index for 100+ documents organized by user type and topic
• docs/DOCUMENTATION_SUMMARY.md - This consolidation's summary

Organization

Reduced root from 35+ files to 7 essential guides:

Root (7)
├── README.md                      # NEW: Main entry point
├── CHANGELOG.md
├── KALSHI_BETTING_GUIDE.md
├── KALSHI_LESSONS_LEARNED.md
├── PORTFOLIO_BETTING.md
├── POSITION_ANALYSIS_README.md
└── SYSTEM_OVERVIEW.md

docs/
├── HISTORY.md                     # NEW: Consolidated timeline
├── EXPERIMENTS.md                 # NEW: All model comparisons
├── BACKTESTING.md                 # NEW: All backtest results
├── GUIDES.md                      # NEW: Complete index
├── dashboard/                     # 7 files + README
├── testing/                       # 3 files + README
└── [19 other guides]

archive/
├── completed_implementations/     # 14 historical summaries + README
└── backtest_reports/             # 6 individual reports + README

Consolidation Details

• 35 implementation summaries → docs/HISTORY.md + archive/completed_implementations/
• 7 model comparison docs → docs/EXPERIMENTS.md + archive/
• 6 sport-specific backtests → docs/BACKTESTING.md + archive/backtest_reports/
• 7 test fix reports → docs/testing/ + archive/completed_implementations/
• 6 dashboard docs → docs/dashboard/

All cross-references updated. README files added to subdirectories for navigation.

Impact

• Root clutter: 80% reduction (35+ → 7 files)
• Discovery: Clear path for new users (README → HISTORY → GUIDES)
• Maintenance: Related docs grouped logically
• Preservation: All 101 markdown files (14,138 lines) retained, just organized

Original prompt

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This section details on the original issue you should resolve

<issue_title>Consolidate Documentation on Current State, Successful and Failed Experiments, and Project History</issue_title>
<issue_description>The documentation is too fragmented. We need to consolidate it into a more manageable state. Please include documentation on project history, successful and failed experiments, etc, etc.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Consolidate Documentation on Current State, Successful and Failed Experiments, and Project History #2

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