docs: Add MANDATORY documentation requirement to copilot instructions

**CRITICAL: Documentation is now a NON-NEGOTIABLE requirement**

- Added ironclad rule: Every git commit MUST update copilot-instructions.md
- NO EXCEPTIONS - this is a real money trading system
- Undocumented fixes = forgotten fixes = financial losses
- Future AI agents need complete context for data integrity

**What must be documented:**
- Bug fixes → Common Pitfalls (symptom, root cause, fix, lesson)
- New features → Architecture Overview, Critical Components
- Database changes → Important fields, filtering requirements
- Config changes → Configuration System section
- Breaking changes → When Making Changes section

**Examples of proper documentation:**
- Common Pitfall #56: Ghost orders (a3a6222)
- Common Pitfall #57: P&L inaccuracy (8e600c8)
- Common Pitfall #55: BlockedSignalTracker (6b00303)

**This is not optional - documentation is part of 'done'**

.github/copilot-instructions.md

@@ -292,6 +292,51 @@ Then observe logs on actual trade:
 
 **Lesson:** One console.log would have exposed the bug immediately.
 
+### CRITICAL: Documentation is MANDATORY (No Exceptions)
+
+**THIS IS A REAL MONEY TRADING SYSTEM - DOCUMENTATION IS NOT OPTIONAL**
+
+**IRON-CLAD RULE:** Every git commit MUST include updated copilot-instructions.md documentation. **NO EXCEPTIONS.**
+
+**Why this is non-negotiable:**
+- This is a financial system handling real money - incomplete documentation = financial losses
+- Future AI agents need complete context to maintain data integrity
+- User relies on documentation to understand what changed and why
+- Undocumented fixes are forgotten fixes - they get reintroduced as bugs
+- Common Pitfalls section prevents repeating expensive mistakes
+
+**MANDATORY workflow for ALL changes:**
+1. Implement fix/feature
+2. Test thoroughly
+3. **UPDATE copilot-instructions.md** (Common Pitfalls, Architecture, etc.)
+4. Git commit code changes
+5. Git commit documentation changes
+6. Push both commits
+
+**What MUST be documented:**
+- **Bug fixes:** Add to Common Pitfalls section with:
+  * Symptom, Root Cause, Real incident details
+  * Complete before/after code showing the fix
+  * Files changed, commit hash, deployment timestamp
+  * Lesson learned for future AI agents
+- **New features:** Update Architecture Overview, Critical Components, API Endpoints
+- **Database changes:** Update Important fields section, add filtering requirements
+- **Configuration changes:** Update Configuration System section
+- **Breaking changes:** Add to "When Making Changes" section
+
+**Recent examples of MANDATORY documentation:**
+- Common Pitfall #56: Ghost orders after external closures (commit a3a6222)
+- Common Pitfall #57: P&L calculation inaccuracy (commit 8e600c8)
+- Common Pitfall #55: BlockedSignalTracker Pyth cache bug (commit 6b00303)
+
+**If you commit code without updating documentation:**
+- User will be annoyed (rightfully so)
+- Future AI agents will lack context
+- Bug will likely recur
+- System integrity degrades
+
+**This is not a suggestion - it's a requirement.** Documentation updates are part of the definition of "done" for any change.
+
 ### Deployment Checklist
 
 **MANDATORY PRE-DEPLOYMENT VERIFICATION:**