fix: de-duplicate four indicators by correcting their definitions (#300)

* fix(core): de-duplicate 3 indicators by correcting their definitions

Behavioral audit found these computed identically to another indicator:

- AverageDrawdown was the mean per-bar under-water fraction = PainIndex.
  Now the conventional average drawdown: mean of the maximum depths of the
  distinct drawdown episodes in the window.
- IntradayIntensity was a cumulative line = the A/D Line (Adl); its normalized
  form is the Chaikin Money Flow (Cmf). Now the raw per-bar Bostian intensity
  volume*(2c-h-l)/(h-l), distinct from both.
- AwesomeOscillatorHistogram was AO - SMA(AO, n) = AcceleratorOscillator. Now
  the AO momentum AO[t] - AO[t-lookback] (the histogram delta); the 3rd
  parameter is reinterpreted from sma_period to lookback (default 1).

Constructor signatures are unchanged, so the bindings keep their API. Core
unit tests rewritten with the new reference values; workspace tests + clippy
green. Binding value-tests and deep-dive docs are updated separately.

* fix(core): redefine AdOscillator as the A/D Oscillator (was a Wad duplicate)

AdOscillator computed the cumulative volume-free Williams A/D line, identical
to the Wad indicator. Redefine it as the Williams A/D *Oscillator*: the same
line minus its 13-bar SMA, so it oscillates around zero (mean-reverting) while
Wad stays the drifting cumulative line for divergence analysis. The canonical
name AdOscillator is now accurate; the trait name() becomes "ADOSC".

Constructor stays no-arg (internal 13-bar signal). Unit tests rewritten and
cross-checked against Wad - SMA(Wad, 13). The native bindings' "WilliamsAD"
alias is renamed to "ADOSC" separately.

* fix(bindings): rename WilliamsAD alias to ADOSC and update value tests

Follows the core de-duplication: the native bindings exposed the Williams A/D
line as 'WilliamsAD', which is now the A/D Oscillator. Rename the Python /
Node.js / WASM alias to 'ADOSC' (regenerated node index.js / index.d.ts) and
update the binding value-tests for the four redefined indicators
(AverageDrawdown episode mean, AwesomeOscillatorHistogram momentum warmup,
the Wad-line reference test now uses ta.Wad()). Python suite and node suite
both pass (pytest all green, node 584/584).

* docs: record indicator de-duplication in README and CHANGELOG

README volume family: 'Williams A/D' -> 'Williams A/D Oscillator', 'Intraday
Intensity Index' -> 'Intraday Intensity'. CHANGELOG [Unreleased] documents the
four redefinitions and the native WilliamsAD -> ADOSC rename as breaking.

* test(core): cover Default impl and drop dead match arm

Codecov flagged AdOscillator::default() (never exercised) and the unreachable
_ => panic!() arm in the AwesomeOscillatorHistogram test. Exercise Default in
the accessors test and rewrite the histogram check as an if-let, removing the
dead arm.

bindings/python/tests/test_new_indicators.py

@@ -634,8 +634,8 @@ CANDLE_SCALAR = {
         lambda: ta.PVI(),
         lambda ind, h, l, c, v: ind.batch(c, v),
     ),
-    "WilliamsAD": (
-        lambda: ta.WilliamsAD(),
+    "ADOSC": (
+        lambda: ta.ADOSC(),
         lambda ind, h, l, c, v: ind.batch(h, l, c),
     ),
     "AnchoredVWAP": (
@@ -1762,7 +1762,7 @@ def test_wad_reference():
     #   TR_l = min(10, 8) = 8 -> delta = 12 - 8 = 4. AD = 4.
     # bar 2: prev=12, today high=11, low=7, close=7 (down day).
     #   TR_h = max(12, 11) = 12 -> delta = 7 - 12 = -5. AD = 4 - 5 = -1.
-    ad = ta.WilliamsAD()
+    ad = ta.Wad()
     high = np.array([11.0, 13.0, 11.0])
     low = np.array([9.0, 8.0, 7.0])
     close = np.array([10.0, 12.0, 7.0])