feat(ml): egreedy-v2 shadow policy — D=12 with profile features (#99)

Ship the scaffolding for #99 (phase B.3 of #81):

- ml/serving: add /score/egreedy/v2, /reward/egreedy/v2, /stats/egreedy/v2
  endpoints (D=12). New feature dims: completion/dismiss rates, mean dwell
  (clipped 10min), preferred-hour alignment (cosine, 1-dim), tip volume (log).
  Separate state file per user (_egreedy_v2.json). /reset clears v2 state too.
- ADR-0012: documents D=7→12 dimension change, normalization choices, shadow
  rollout protocol, and promotion gate (offline sim win per ADR-0002).
- recommender.ts: register egreedy-v2-shadow in shadow-policy map (disabled by
  default). When enabled, calls /score/egreedy/v2 fire-and-forget and publishes
  shadow:egreedy-v2-shadow serve signal. No reward to shadow — sim is the gate.
- sim runner/personas: personas carry synthetic profile_features per persona;
  _call_score/_call_reward thread profile_features through (None-safe for v1/linucb).
- 18 new Python tests; all 56 Python + 170 TS tests pass.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

services/api/src/routes/recommender.ts

@@ -47,8 +47,8 @@ export const _clearCandidateCacheForTests = () => {
 // Shadow-policy registry
 // ---------------------------------------------------------------------------
 const shadowPolicies = new Map<string, { active: boolean }>([
-  // Example: enable random as a shadow baseline
-  // ('random-shadow', { active: true }),
+  // egreedy-v2 (D=12, profile features) — disabled until sim gate per ADR-0012
+  ['egreedy-v2-shadow', { active: false }],
 ]);
 
 export function getShadowPolicies() {
@@ -296,6 +296,42 @@ router.post('/recommend', requireAuth, async (req: AuthenticatedRequest, res: Re
         policy: `shadow:${name}`,
         servedAt,
       });
+    } else if (name === 'egreedy-v2-shadow') {
+      // Call v2 endpoint with the same payload used for the active policy.
+      // No reward is delivered — offline sim is the reward measurement for shadow.
+      void (async () => {
+        try {
+          const body = {
+            user_id: req.userId!,
+            candidates: allCandidates.map((t) => ({
+              id: t.id,
+              content: t.content,
+              source: t.source,
+              source_id: t.sourceId ?? null,
+              features: t.features,
+            })),
+            context: { hour_of_day: hour, day_of_week: dayOfWeek },
+            profile_features: profile,
+          };
+          const res = await fetch(`${config.ML_SERVING_URL}/score/egreedy/v2`, {
+            method: 'POST',
+            headers: { 'Content-Type': 'application/json' },
+            body: JSON.stringify(body),
+            signal: AbortSignal.timeout(3000),
+          });
+          if (res.ok) {
+            const data = (await res.json()) as { tip_id: string };
+            bus.publish('signals.tip.served', {
+              userId: req.userId!,
+              tipId: data.tip_id,
+              policy: `shadow:${name}`,
+              servedAt,
+            });
+          }
+        } catch {
+          // shadow is best-effort
+        }
+      })();
     }
   }