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.go

@@ -145,8 +145,26 @@ func abilityModifier(score int) int {
 	return diff/2 - 1
 }
 
+// phase5BHPMult is the Phase 5-B HP-floor multiplier. Applied uniformly
+// in computeMaxHP so every class/level scales together — preserves the
+// class-balance harness's parity assertions (which test in-tier spread,
+// not absolute win rates) while lifting durability enough to land the
+// expedition harness in the "fairly breezy with some death" band the
+// user chose for Phase 5-B. See gogobee_expedition_difficulty.md for
+// the sweep that picked 1.5 (gear-bonus floor +3, HP ×1.5 → T1=85 T2=73
+// T3=60 T4=78 T5=81 mean completion at the tier-centerline cell).
+//
+// Bumping this changes the *persisted* HPMax for new characters and for
+// existing characters on their next computeMaxHP recall (level-up,
+// character reset, bootstrap refresh). The Phase 5-B bootstrap
+// (bootstrap_phase5b_hp.go) walks the dnd_character table once at
+// startup to refresh stale rows.
+const phase5BHPMult = 1.5
+
 // computeMaxHP — D&D5e style. L1: full HP die + CON mod (min 1).
 // Per level after: average HP die (roundup of die/2 + 1) + CON mod.
+// The result is scaled by phase5BHPMult — see that constant for the
+// difficulty-pass motivation.
 func computeMaxHP(class DnDClass, conMod, level int) int {
 	ci, ok := classInfo(class)
 	if !ok {
@@ -163,7 +181,12 @@ func computeMaxHP(class DnDClass, conMod, level int) int {
 		}
 		hp += gain
 	}
-	return hp
+	// Phase 5-B player power floor — round to nearest int.
+	scaled := int(float64(hp)*phase5BHPMult + 0.5)
+	if scaled < 1 {
+		scaled = 1
+	}
+	return scaled
 }
 
 // computeAC — Phase 1 baseline. Equipment-derived AC arrives in Phase 4