Lift caster trailers: concentration re-tick + Josie caster-aid bootstraps

Diagnosed a cleric "death loop" (L14 dying at T2/T3 bosses while
over-levelled): the boss isn't overtuned — caster sustained DPS is
under-delivered, compounded by a fragile healer build.

Engine fix — concentration AOE re-tick:
- Concentration damage spells (spirit_guardians, heat_metal, spike_growth,
  call_lightning, flaming_sphere) now tick the enemy every round at
  round_end instead of resolving as a one-shot, via a new
  CombatStatuses.ConcentrationDmg armed on cast and round-tripped through
  the turn engine. Closes the long-tracked turn-engine concentration gap;
  the burst still lands the casting round, then the aura lingers.
- Sim picker skips re-casting an already-active aura (models competent play
  and prevents a burst+aura double-dip). Re-baseline (n=30 sweep + n=100
  confirm): bard +47pp T3 (heat_metal), druid +3-7, cleric/mage flat,
  fighter unchanged — no regressions.

Player-data bootstraps (idempotent, run once on Init):
- bootstrapCasterSpellBackfill: ensureSpellsForCharacter only seeds an empty
  book, so defaults added after a character's roll never reach it. Backfill
  missing defaults into known+prepared for existing casters (gives the
  affected cleric inflict_wounds + a working healing_word, since her
  healing_word_spell is a dead alias).
- bootstrapGrantStarterPet: one-off L10 pet for an endgame player who never
  got the morning arrival roll; adds per-round proc damage + deflect.
- TestScenario_JosieCasterAid verifies both against a copy of the live DB,
  incl. idempotency.

Also fix a pre-existing wall-clock flake in
TestFireBriefings_EventAnchoredActivePlayerDelivers (start_date defaulted to
real now, filtering the row out when the suite runs after 06:00 UTC).

internal/plugin/expedition_sim.go

@@ -919,7 +919,12 @@ func (p *AdventurePlugin) pickAutoCombatAction(uid id.UserID, sess *CombatSessio
 		if id := simPickSpiritualWeapon(c, uid, sess); id != "" {
 			return "cast", id
 		}
-		if id := simPickSpell(c, uid); id != "" {
+		// Once a concentration aura is up, a competent caster maintains it and
+		// attacks (or casts a non-concentration spell) rather than burning a
+		// slot to re-arm the same aura — so the picker excludes concentration
+		// spells while one is active.
+		auraActive := sess.Statuses.ConcentrationDmg > 0
+		if id := simPickSpell(c, uid, auraActive); id != "" {
 			return "cast", id
 		}
 	}
@@ -1008,7 +1013,7 @@ func simPickSpiritualWeapon(c *DnDCharacter, uid id.UserID, sess *CombatSession)
 //   - Among feasible candidates, prefer higher slot level (preserves
 //     high-slot supremacy and burns the big slots first); tie-break on
 //     expected damage from the dice string.
-func simPickSpell(c *DnDCharacter, uid id.UserID) string {
+func simPickSpell(c *DnDCharacter, uid id.UserID, auraActive bool) string {
 	known, err := listKnownSpells(uid)
 	if err != nil || len(known) == 0 {
 		return ""
@@ -1037,6 +1042,11 @@ func simPickSpell(c *DnDCharacter, uid id.UserID) string {
 		if sp.CastTime == CastReaction {
 			continue
 		}
+		// An aura is already ticking — don't re-arm it; prefer attacks or a
+		// non-concentration spell this turn.
+		if auraActive && sp.Concentration {
+			continue
+		}
 		onList := false
 		for _, cl := range sp.Classes {
 			if cl == c.Class {