feat(dynamics): add PlusDI, MinusDI, PlusDM, MinusDM indicators

Complete thin Dx-composition wrapper indicators with full test coverage:

- PlusDi/MinusDi: Directional Indicator wrappers (DiPlus/DiMinus from Dx)
- PlusDm/MinusDm: Directional Movement wrappers (DmPlus/DmMinus from Dx)
- Individual validation tests per indicator directory (TALib, Skender, bounds)
- Combined unit tests (DiDm.Tests.cs) and validation tests (DiDm.Validation.Tests.cs)
- Quantower wrappers + tests for all 4 indicators
- PineScript v6 implementations with compensated RMA
- Normalized .md documentation for all indicators and categories
- 182 tests passing, 0 failures

lib/errors/mpe/Mpe.md

@@ -1,5 +1,7 @@
 # MPE: Mean Percentage Error
 
+> *MAPE tells you how wrong you are; MPE tells you which direction you're wrong in.*
+
 | Property         | Value                            |
 | ---------------- | -------------------------------- |
 | **Category**     | Error Metric                        |
@@ -16,8 +18,6 @@
 - Requires 1 bar of warmup before first valid output (IsHot = true).
 - Validated against TA-Lib, Skender, and Tulip reference implementations where available.
 
-> "MAPE tells you how wrong you are; MPE tells you which direction you're wrong in."
-
 Mean Percentage Error measures the average percentage difference between actual and predicted values while preserving the sign. Unlike MAPE, which takes absolute values, MPE reveals systematic bias in predictions—whether a model consistently over-predicts or under-predicts.
 
 ## Architecture & Physics