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/channels/regchannel/regchannel.md

@@ -1,5 +1,7 @@
 # REGCHANNEL: Linear Regression Channel
 
+> *A regression line flanked by standard error bands — the channel where statistics meets price trajectory.*
+
 | Property         | Value                            |
 | ---------------- | -------------------------------- |
 | **Category**     | Channel                        |
@@ -101,45 +103,6 @@ $$
 
 For $n \geq 2$, $D > 0$ always, ensuring numerical stability.
 
-### Pseudo-code
-
-```
-function regchannel(source[], period, multiplier):
-    buf = ring_buffer(period)
-    sum_x  = period * (period - 1) / 2
-    sum_x2 = period * (period - 1) * (2 * period - 1) / 6
-    denom  = period * sum_x2 - sum_x * sum_x
-
-    for each bar t:
-        buf.add(source[t])
-        n = buf.count
-
-        // pass 1: accumulate sums for regression
-        sum_y  = 0
-        sum_xy = 0
-        for i = 0 to n-1:
-            y = buf[i]
-            sum_y  += y
-            sum_xy += i * y
-
-        slope     = (n * sum_xy - sum_x * sum_y) / denom
-        intercept = (sum_y - slope * sum_x) / n
-        middle    = slope * (n - 1) + intercept
-
-        // pass 2: residual standard deviation
-        ssr = 0
-        for i = 0 to n-1:
-            predicted = slope * i + intercept
-            residual  = buf[i] - predicted
-            ssr += residual * residual
-
-        stddev = sqrt(ssr / n)
-        upper  = middle + multiplier * stddev
-        lower  = middle - multiplier * stddev
-
-        emit (upper, middle, lower)
-```
-
 ### Output Interpretation
 
 | Output | Interpretation |