Phase 5b: player power floor + Phase-3 winners shipped to live

Closes the 'fairly breezy with some death' target the user picked
for Phase 5. Five-piece ship; Phase 1 matrix lands T1 88%, T2 74%,
T4 72%, T5 ~57% in or above band. T3 remains the design hump at
~45% (manor 39, underforge 47) — Wraith promotion to elite was
already done in Phase 4-B, the remaining standard-pool deaths are
the irreducible part of T3.

Pieces:
  1. computeMaxHP × 1.5 (phase5BHPMult in dnd.go). Uniform across
     class/level so the class-balance harness's in-tier parity
     assertion stays green. Bootstrap (bootstrap_phase5b_hp.go)
     refreshes hp_max for existing characters at startup;
     idempotent via db.JobCompleted. hp_current is bumped by the
     same delta so a full-HP character stays at full.
  2. applyPhase5BPlayerFloor (dnd_combat.go): +3 AC, +3 AttackBonus,
     +3 weapon.MagicBonus (damage). Applied at the END of
     applyDnDEquipmentLayer (after computeArmorAC's AC override)
     and inside buildHarnessPlayer so live and harness measurement
     match.
  3. Elite bracket 19 → 23 (resolveCombatInterrupt). Case order
     puts Elite (≥23) before Patrol (≥22) so a 23+ total prefers
     the single dangerous fight. Elite is now effectively a
     high-threat event reachable only via the +1-per-20-threat-
     above-40 mod — Phase 4-B's elite-pool monsters still appear,
     just less often.
  4. dailyThreatDrift base 3 → 1. Slows the threat clock so
     players have the days they need before threat tips zones
     into the new 23+ elite band.
  5. applyDailyBurn default → 50% (phase5BDailyBurnRatePct). Also
     applied in the temporal-override branch in
     dnd_expedition_cycle.go so tidal / unraveling days scale by
     the same 0.5× — otherwise those days would be
     disproportionately harsh against the new baseline.

The harness's expedition_balance.go reads phase5BDailyBurnRatePct
as the default-burn fallback when the override knob is zero, so
Phase 1 matrix measurements now reflect what live players
experience.

Test debt: 13 pinned-numbers unit tests across combat_stats_test,
dnd_test, dnd_xp_test, dnd_equipment_profiles_test,
dnd_expedition_supplies_test, dnd_expedition_cycle_test,
dnd_expedition_extract_test, dnd_expedition_region_cmd_test,
dnd_expedition_combat_test, dnd_expedition_threat_test,
dnd_expedition_temporal_test, expedition_balance_test were
pinning pre-Phase-5-B baselines; updated with comments noting
the cause. Class-balance suite stayed green (uniform buff
preserves spread).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/plugin/dnd_expedition_cycle_test.go

@@ -66,8 +66,10 @@ func TestDeliverBriefing_AdvancesDayAndBurnsSupplies(t *testing.T) {
 	if got.CurrentDay != 2 {
 		t.Errorf("current_day = %d, want 2", got.CurrentDay)
 	}
-	if got.Supplies.Current != 9 {
-		t.Errorf("supplies = %v, want 9", got.Supplies.Current)
+	// Phase 5-B: applyDailyBurn scales by phase5BDailyBurnRatePct=50, so
+	// raw burn 1 × 0.5 = 0.5 SU. Current 10 - 0.5 = 9.5.
+	if got.Supplies.Current != 9.5 {
+		t.Errorf("supplies = %v, want 9.5", got.Supplies.Current)
 	}
 	if got.LastBriefingAt == nil {
 		t.Error("LastBriefingAt should be set")
@@ -105,8 +107,9 @@ func TestDeliverBriefing_HarshConditionsBurnFaster(t *testing.T) {
 		t.Fatal(err)
 	}
 	got, _ := getExpedition(exp.ID)
-	if got.Supplies.Current != 8 { // 1 base × 2 harsh = 2 SU
-		t.Errorf("harsh burn supplies = %v, want 8", got.Supplies.Current)
+	// Phase 5-B: 1 base × 2 harsh × phase5B 50% = 1 SU; current 10 - 1 = 9.
+	if got.Supplies.Current != 9 {
+		t.Errorf("harsh burn supplies = %v, want 9", got.Supplies.Current)
 	}
 }