ui/phase-27: root-cause aggregation of duplicate (race, className) rows

Legacy reports list the same `(race, className)` pair across several
roster rows; the engine likewise creates one ShipGroup per arrival.
Both the legacy parser and `TransformBattle` were keyed on shipClass
without summing — only the last row / group's counts survived, so a
protocol's destroy count appeared to exceed the recorded initial
roster. The UI worked around this with phantom-frame logic.

Both parser and engine now SUM `Number`/`NumberLeft` across rows /
groups sharing the same class; the phantom-frame workaround is gone.
KNNTS041 turn 41 planet #7 reconciles: `Nails:pup` 1168 initial −
86 survivors = 1082 destroys.

The engine's previously latent nil-map write on `bg.Tech` (would
have paniced on any group with non-empty Tech) is fixed in the same
patch — it blocked the aggregation regression test.

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

game/internal/controller/battle_transform.go

@@ -18,10 +18,35 @@ func TransformBattle(c *Cache, b *Battle) *report.BattleReport {
 
 	cacheShipClass := make(map[uuid.UUID]int)
 	cacheRaceName := make(map[uuid.UUID]int)
+	processedGroup := make(map[int]bool)
 
 	addShipGroup := func(groupId int, inBattle bool) int {
 		shipClass := c.ShipGroupShipClass(groupId)
 		sg := c.ShipGroup(groupId)
+		// Several ship-groups of the same race/class can take part
+		// in the same battle (different tech upgrades, arrivals from
+		// different planets, …). They share a single
+		// BattleReportGroup entry keyed by ShipClass.ID — when a
+		// later group lands on a cached class we add its Number and
+		// NumberLeft into the existing entry instead of dropping
+		// them, so the protocol's per-class destroy counts reconcile
+		// with the recorded totals. `processedGroup` guards against
+		// double-counting a single groupId across multiple shots in
+		// the protocol — `ship()` runs on every attacker and defender
+		// reference, the merge must happen once per groupId.
+		if existing, ok := cacheShipClass[shipClass.ID]; ok {
+			if !processedGroup[groupId] {
+				bg := r.Ships[existing]
+				bg.Number += b.InitialNumbers[groupId]
+				bg.NumberLeft += sg.Number
+				if inBattle {
+					bg.InBattle = true
+				}
+				r.Ships[existing] = bg
+				processedGroup[groupId] = true
+			}
+			return existing
+		}
 		itemNumber := len(r.Ships)
 		bg := &report.BattleReportGroup{
 			Race:         c.g.Race[c.RaceIndex(sg.OwnerID)].Name,
@@ -31,22 +56,19 @@ func TransformBattle(c *Cache, b *Battle) *report.BattleReport {
 			ClassName:    shipClass.Name,
 			LoadType:     sg.CargoString(),
 			LoadQuantity: report.F(sg.Load.F()),
+			Tech:         make(map[string]report.Float, len(sg.Tech)),
 		}
 		for t, v := range sg.Tech {
 			bg.Tech[t.String()] = report.F(v.F())
 		}
 		r.Ships[itemNumber] = *bg
 		cacheShipClass[shipClass.ID] = itemNumber
+		processedGroup[groupId] = true
 		return itemNumber
 	}
 
 	ship := func(groupId int) int {
-		shipClass := c.ShipGroupShipClass(groupId)
-		if v, ok := cacheShipClass[shipClass.ID]; ok {
-			return v
-		} else {
-			return addShipGroup(groupId, true)
-		}
+		return addShipGroup(groupId, true)
 	}
 
 	race := func(groupId int) int {