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/volume/mfi/Mfi.md

@@ -1,5 +1,7 @@
 # MFI: Money Flow Index
 
+> *Volume confirms price, but money flow confirms intent.*
+
 | Property         | Value                            |
 | ---------------- | -------------------------------- |
 | **Category**     | Volume                        |
@@ -16,8 +18,6 @@
 - Requires `> period` bars of warmup before first valid output (IsHot = true).
 - Validated against TA-Lib, Skender, and Tulip reference implementations where available.
 
-> "Volume confirms price, but money flow confirms intent." — Gene Quong & Avrum Soudack
-
 Money Flow Index is the volume-weighted cousin of RSI. While RSI measures the momentum of price changes alone, MFI incorporates volume to determine whether the price movement has conviction behind it. The result is an oscillator that can identify when strong hands are accumulating or distributing.
 
 The innovation of MFI is answering not just "Is price going up?" but "Is significant money pushing price up?" A stock rising on thin volume produces a different MFI reading than one rising on heavy institutional participation.