replace EV activation gate with cross-sectional 12-1 momentum ranking

The 5-year backtest confirmed the EV gate adds negative value (high threshold =
worst expectancy) and that 12-1 month momentum is the one price signal with a
plausible, right-signed cross-sectional IC (~0.05). So "qualified" now means:
clears the R:R + confidence floors AND the ticker ranks in the top
`min_momentum_percentile` of the universe by 12-1 momentum that week.

- qualification.py: drop expected_value_r / the EV gate; add a momentum-percentile
  gate (duck-typed `momentum_percentile`, only enforced when attached + threshold
  set, else defers to floors). Mirrored in frontend qualification.ts.
- activation config/schema: min_expected_value -> min_momentum_percentile
  (default 80 = top quintile). ActivationSettings, DashboardPage (ranks/【shows】
  momentum instead of EV), and the BacktestPanel sweep follow.
- backtest: rank each ISO week's universe by 12-1 momentum, assign a percentile,
  and qualify the top slice; the sweep now sweeps the percentile cutoff.

Also offload the backtest's per-ticker compute to a worker thread so the heavy
~5y run no longer blocks the API event loop (the "backend offline" flicker).

Production setups don't carry momentum_percentile yet — wiring the scanner to
attach it (a universe momentum-rank step) is the next step; until then the live
gate defers to floors while the backtest measures the momentum selection. 330
backend tests pass; frontend build clean.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/lib/qualification.ts

@@ -13,21 +13,6 @@ export function primaryTargetProbability(setup: TradeSetup): number | null {
   return setup.targets?.length ? bestTargetProbability(setup) : null;
 }
 
-/**
- * Expected value per unit of risk, in R. Probability-weighted payoff:
- *   EV = p·(R:R) − (1 − p)
- * where p is the primary target's hit probability. This is the single "is this
- * worth taking" number — it rewards both a good payoff ratio and a likely
- * target, so a fat-but-improbable target can't outrank a solid, probable one.
- * Returns null when no target probability is known.
- */
-export function expectedValueR(setup: TradeSetup): number | null {
-  const prob = primaryTargetProbability(setup);
-  if (prob == null) return null;
-  const p = prob / 100;
-  return p * setup.rr_ratio - (1 - p);
-}
-
 /** R:R recomputed from the current price (0 if no reward/risk left). */
 export function liveRiskReward(setup: TradeSetup, currentPrice: number): number {
   const reward = setup.direction === 'long' ? setup.target - currentPrice : currentPrice - setup.target;
@@ -48,10 +33,12 @@ export function qualifiesSetup(setup: TradeSetup, config: ActivationConfig): boo
     return false;
   }
   if ((setup.confidence_score ?? 0) < config.min_confidence) return false;
-  // Expected value (R) is the core gate. Only enforced when computable — setups
-  // without target probabilities defer to the R:R + confidence floors above.
-  const ev = expectedValueR(setup);
-  if (ev != null && ev < config.min_expected_value) return false;
+  // Cross-sectional momentum is the core selection — only enforced when a
+  // percentile is attached and a threshold is set; otherwise defer to the floors.
+  if (config.min_momentum_percentile > 0 && setup.momentum_percentile != null
+      && setup.momentum_percentile < config.min_momentum_percentile) {
+    return false;
+  }
   if (config.require_high_conviction && !HIGH_CONVICTION_ACTIONS.has(setup.recommended_action ?? '')) {
     return false;
   }
@@ -64,7 +51,9 @@ export function qualifiesSetup(setup: TradeSetup, config: ActivationConfig): boo
 
 /** Short human summary of the active gate, e.g. for tooltips/labels. */
 export function activationSummary(config: ActivationConfig): string {
-  const parts = [`EV ≥ ${config.min_expected_value.toFixed(2)}R`, `R:R ≥ ${config.min_rr.toFixed(1)}`, `conf ≥ ${config.min_confidence.toFixed(0)}%`];
+  const parts = [];
+  if (config.min_momentum_percentile > 0) parts.push(`top ${(100 - config.min_momentum_percentile).toFixed(0)}% momentum`);
+  parts.push(`R:R ≥ ${config.min_rr.toFixed(1)}`, `conf ≥ ${config.min_confidence.toFixed(0)}%`);
   if (config.require_high_conviction) parts.push('high-conviction');
   if (config.exclude_conflicts) parts.push('clean');
   if (config.min_target_probability > 0) parts.push(`target ≥ ${config.min_target_probability.toFixed(0)}%`);

frontend/src/lib/types.ts

@@ -134,6 +134,7 @@ export interface TradeSetup {
   outcome_date: string | null;
   evaluated_at: string | null;
   current_price: number | null;
+  momentum_percentile?: number | null;
   recommendation_summary?: RecommendationSummary;
 }
 
@@ -158,7 +159,7 @@ export interface PerformanceStats {
 
 // Activation gate: what counts as an actionable signal
 export interface ActivationConfig {
-  min_expected_value: number;
+  min_momentum_percentile: number;
   min_rr: number;
   min_confidence: number;
   min_target_probability: number;
@@ -221,7 +222,7 @@ export interface BacktestCalibrationRow {
 }
 
 export interface BacktestSweepRow extends BacktestBucket {
-  min_expected_value: number;
+  min_momentum_percentile: number;
 }
 
 export interface BacktestSignalEvalRow {
@@ -244,7 +245,7 @@ export interface BacktestReport {
   overall_qualified: BacktestBucket;
   overall_all: BacktestBucket;
   by_direction: Record<string, BacktestBucket>;
-  min_expected_value: number;
+  min_momentum_percentile: number;
   sweep: BacktestSweepRow[];
   calibration: BacktestCalibrationRow[];
   signal_eval?: BacktestSignalEvalRow[];