feat(rl): reset_session_state regime boundary policy (F1.7)

Extends reset_session_state with 8 new regime_observer slot resets per
spec section "Regime observer reset policy at fold/eval boundaries":

- Transient state (FLAG/DURATION/TIMEOUT) → 0
- RECOVERY_FACTOR → 1.0
- TAIL_EVENT_RECENCY → 1e6 sentinel
- KELLY_EPS_RECOVERY_LIVE → 0.50 (= ε_max)
- PREV_WORST_PNL → 0 (CRITICAL — prevents spurious 3σ tail at boundary)
- POPART_MAX_ABS_REWARD_EMA → 0 (F4 envelope reset)

Welford state (M2/MEAN/COUNT) intentionally NOT reset — variance of
session_pnl_change is regime-invariant per pearl_adaptive_carryover_discipline.

Issue γ fix: without PREV_WORST_PNL reset, the first regime_observer call
after a fold boundary would see Δworst = 0 - (-\$15k_train) = +\$15k, fire
a spurious 3σ tail event, and peg ε_recovery at ε_min for 100 steps.

crates/ml-alpha/src/trainer/integrated.rs

@@ -3059,6 +3059,25 @@ impl IntegratedTrainer {
             (crate::rl::isv_slots::RL_REWARD_CLAMP_CLIP_RATE_EMA_INDEX,  0.0_f32),
             // v9 — arm the defensive warmup window.
             (crate::rl::isv_slots::RL_EVAL_WARMUP_REMAINING_INDEX,   warmup_steps),
+            // Regime observer boundary policy (F1.7 — spec 2026-05-31 v3,
+            // [[pearl_adaptive_carryover_discipline]]):
+            //   - Transient state (FLAG/DURATION/TIMEOUT) → 0
+            //   - RECOVERY_FACTOR → 1.0 (no recent tail; ε = ε_max)
+            //   - TAIL_EVENT_RECENCY → 1e6 sentinel ("no tails seen yet")
+            //   - KELLY_EPS_RECOVERY_LIVE → 0.50 (= ε_max default)
+            //   - PREV_WORST_PNL → 0 (CRITICAL — must align with the just-reset
+            //     session_pnl_worst above to prevent spurious 3σ tail event)
+            //   - POPART_MAX_ABS_REWARD_EMA → 0 (F4 envelope reset)
+            //   - Welford state (M2/MEAN/COUNT) intentionally NOT reset — the
+            //     variance of session_pnl_change is regime-invariant.
+            (crate::rl::isv_slots::RL_REGIME_DEAD_ZONE_FLAG_INDEX,           0.0_f32),
+            (crate::rl::isv_slots::RL_REGIME_DEAD_ZONE_DURATION_INDEX,       0.0_f32),
+            (crate::rl::isv_slots::RL_REGIME_DEAD_ZONE_TIMEOUT_FLAG_INDEX,   0.0_f32),
+            (crate::rl::isv_slots::RL_REGIME_TAIL_EVENT_RECENCY_INDEX,       1.0e6_f32),
+            (crate::rl::isv_slots::RL_REGIME_RECOVERY_FACTOR_INDEX,          1.0_f32),
+            (crate::rl::isv_slots::RL_KELLY_EPS_RECOVERY_LIVE_INDEX,         0.50_f32),
+            (crate::rl::isv_slots::RL_REGIME_PREV_WORST_PNL_INDEX,           0.0_f32),
+            (crate::rl::isv_slots::RL_POPART_MAX_ABS_REWARD_EMA_INDEX,       0.0_f32),
         ] {
             let mut args = RawArgs::new();
             args.push_ptr(self.isv_dev_ptr);