The WilliamsR implementation had build errors and lacked consistency across series, buffer, and stream styles. The StreamHub test also needed comprehensive rollback validation following the canonical EMA/ADX pattern.

Changes

Build Error Fixes

• WilliamsR.StreamHub.cs
  • Fixed type mismatch: Changed RollingWindowMax/Min<decimal> to RollingWindowMax/Min<double>
  • Fixed undefined variable: Changed l to low
  • Removed unused variable o (open)
  • Fixed typo: Nan2Null() → NaN2Null() in BufferList

Consistency Improvements

Implemented consistent composite lookback buffer pattern across all three styles:

• Series: Already uses CalcStoch internally (no changes needed)
• BufferList: Now delegates to StochList internally
  • Eliminates duplicate HLC buffer management code
  • Uses Fast Stochastic parameters (lookback, signal=1, smooth=1)
  • Converts Stochastic %K to Williams %R by subtracting 100
• StreamHub: Maintains direct O(1) RollingWindow implementation for performance
  • Added comment clarifying relationship to Stochastic formula
  • Uses same efficient window pattern as StochHub

All three styles now consistently express: Williams %R = Stochastic %K - 100

Enhanced StreamHub Test

• Enhanced QuoteObserver_WithWarmupLateArrivalAndRemoval_MatchesSeriesExactly()
  • Prefill 20 quotes before observer initialization (warmup coverage)
  • Skip quote at index 80, stream remaining quotes
  • Resend duplicates at indices 101-104
  • Insert skipped quote and verify against original series
  • Remove quote using base class removeAtIndex constant (495), not hardcoded value
  • Compare against RevisedQuotes from base class
  • Add strict ordering verification with BeEquivalentTo(..., o => o.WithStrictOrdering())
  • Add proper cleanup (Unsubscribe(), EndTransmission())

Test Pattern

Now matches canonical EMA/ADX StreamHub test structure:

// Prefill warmup
quoteHub.Add(Quotes.Take(20));
WilliamsRHub observer = quoteHub.ToWilliamsRHub(lookbackPeriods);

// Stream with skip and duplicates
for (int i = 20; i < length; i++) {
    if (i == 80) { continue; }
    quoteHub.Add(Quotes[i]);
    if (i is > 100 and < 105) { quoteHub.Add(Quotes[i]); }
}

// Validate Insert/Remove operations
quoteHub.Insert(Quotes[80]);
actuals.Should().BeEquivalentTo(expectedOriginal, o => o.WithStrictOrdering());

quoteHub.Remove(Quotes[removeAtIndex]);
actuals.Should().BeEquivalentTo(RevisedQuotes.ToWilliamsR(lookbackPeriods), o => o.WithStrictOrdering());

Verification

• ✅ Build succeeds (0 errors, 0 warnings)
• ✅ All tests pass (2078 tests)
• ✅ Code formatting verified
• ✅ Markdown linting passes

Addresses follow-on task T177 from #1723.

Custom agent used: streamhub
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• Fixes add rollback validation tests for WilliamsR StreamHub #1725

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