docs: Add mandatory instruction update step to When Making Changes

- Added step 14: UPDATE COPILOT-INSTRUCTIONS.MD (MANDATORY)
- Ensures future agents have complete context for data integrity
- Examples: database fields, filtering requirements, analysis exclusions
- Prevents breaking changes to analytics and indicator optimization
- Meta-documentation: instructions about updating instructions

.github/copilot-instructions.md

@@ -1493,6 +1493,17 @@ if (!enabled) {
     - Backlog (📥) → Planning (📋) → In Progress (🚀) → Complete (✅)
     - Keep Deck in sync with actual work - it's the visual roadmap tracker
     - Documentation: `docs/NEXTCLOUD_DECK_SYNC.md`
+14. **UPDATE COPILOT-INSTRUCTIONS.MD (MANDATORY):** After implementing ANY significant feature or system change:
+    - Document new database fields and their purpose
+    - Add filtering requirements (e.g., manual vs TradingView trades)
+    - Update "Important fields" sections with new schema changes
+    - Add new API endpoints to the architecture overview
+    - Document data integrity requirements (what must be excluded from analysis)
+    - Add SQL query patterns for common operations
+    - Update "When Making Changes" section with new patterns learned
+    - Create reference docs in `docs/` for complex features (e.g., `MANUAL_TRADE_FILTERING.md`)
+    - **WHY:** Future AI agents need complete context to maintain data integrity and avoid breaking analysis
+    - **EXAMPLES:** signalSource field for filtering, MAE/MFE tracking, phantom trade detection
 
 ## Development Roadmap