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/bootstrap_phase5b_hp.go

@@ -0,0 +1,95 @@
+package plugin
+
+import (
+	"log/slog"
+
+	"gogobee/internal/db"
+)
+
+// bootstrapPhase5BHPRefresh recomputes hp_max for every dnd_character
+// row after the Phase 5-B HP multiplier (phase5BHPMult in dnd.go)
+// shipped. Without this, existing characters keep their pre-Phase-5-B
+// hp_max until something else recomputes it (level-up, character reset,
+// migration), so the durability lift wouldn't reach live players for
+// weeks. See gogobee_expedition_difficulty.md Phase 5-B.
+//
+// Pattern mirrors bumpDexFloorForExistingCharacters: enumerate, derive
+// new value, update only rows where the new value differs. hp_current
+// is bumped by the same delta so a full-HP character stays at full HP
+// after the bump; a wounded character keeps the same absolute wound
+// (e.g. -7 HP) so the lift only raises the *ceiling*, not the present
+// HP — players don't get a free heal on top of a permanent buff.
+//
+// Idempotent via the db.JobCompleted gate. The job key is bumped if we
+// ever ship a second HP-curve change so the migration runs once per
+// shipped change.
+func bootstrapPhase5BHPRefresh() {
+	const jobName = "phase5b_hp_refresh_v1"
+	if db.JobCompleted(jobName, "once") {
+		return
+	}
+
+	d := db.Get()
+	rows, err := d.Query(`
+		SELECT user_id, class, con_score, dnd_level, hp_max, hp_current
+		FROM dnd_character WHERE dnd_level > 0`)
+	if err != nil {
+		slog.Error("phase5b hp refresh: enumerate failed", "err", err)
+		return
+	}
+	defer rows.Close()
+
+	type row struct {
+		userID    string
+		class     DnDClass
+		conScore  int
+		level     int
+		hpMax     int
+		hpCurrent int
+	}
+	var batch []row
+	for rows.Next() {
+		var r row
+		var classStr string
+		if err := rows.Scan(&r.userID, &classStr, &r.conScore, &r.level, &r.hpMax, &r.hpCurrent); err != nil {
+			slog.Warn("phase5b hp refresh: scan failed", "err", err)
+			continue
+		}
+		r.class = DnDClass(classStr)
+		batch = append(batch, r)
+	}
+
+	refreshed := 0
+	for _, r := range batch {
+		conMod := abilityModifier(r.conScore)
+		newMax := computeMaxHP(r.class, conMod, r.level)
+		if newMax <= r.hpMax {
+			// Either already at/above target (re-runs, or the row was
+			// hand-edited above formula), or the formula change reduced
+			// HP for this class — leave it alone in that case so we
+			// never *lower* a player's HP via bootstrap.
+			continue
+		}
+		delta := newMax - r.hpMax
+		newCurrent := r.hpCurrent + delta
+		if newCurrent > newMax {
+			newCurrent = newMax
+		}
+		if newCurrent < 1 {
+			newCurrent = 1
+		}
+		if _, err := d.Exec(`UPDATE dnd_character
+			SET hp_max = ?, hp_current = ?, updated_at = CURRENT_TIMESTAMP
+			WHERE user_id = ?`,
+			newMax, newCurrent, r.userID); err != nil {
+			slog.Warn("phase5b hp refresh: update failed", "user", r.userID, "err", err)
+			continue
+		}
+		refreshed++
+	}
+
+	db.MarkJobCompleted(jobName, "once")
+	if refreshed > 0 {
+		slog.Info("phase5b hp refresh: refreshed character HPMax to Phase 5-B floor", "count", refreshed)
+	}
+}