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>

tools/local-dev/legacy-report/parser_test.go

@@ -533,6 +533,106 @@ func TestParseBattles(t *testing.T) {
 	}
 }
 
+// TestParseBattleAggregatesDuplicateClasses guards against the
+// regression that produced the original "phantom destroys" symptom:
+// the same `(race, className)` pair appearing on multiple roster
+// rows must collapse into a single BattleReportGroup whose `Number`
+// (the "#" column, initial ship count) and `NumberLeft` (the "L"
+// column, survivors) are the sums across rows. Without the
+// aggregation only the last row's counts survived and the protocol's
+// destroy count dwarfed the recorded initial count (e.g. KNNTS041
+// turn-41 planet #7 lists `pup` seven separate times: 99 + 105 + 291 +
+// 287 + 166 + 132 + 88 = 1168 ships, 86 survivors, 1082 destroys).
+func TestParseBattleAggregatesDuplicateClasses(t *testing.T) {
+	in := strings.Join([]string{
+		"Race Report for Galaxy PLUS Turn 1",
+		"",
+		"Battle at (#7) B-007",
+		"",
+		"Foo Groups",
+		"",
+		" #  T          D    W  S  C  T  Q  L",
+		" 3  Drone    1.0  1.0  0  0  -  0  1  In_Battle",
+		" 4  Drone    1.2  1.0  0  0  -  0  2  In_Battle",
+		"10  Cruiser  3.0  2.0  0  0  -  0  9  In_Battle",
+		"",
+		"Bar Groups",
+		"",
+		"#  T          D    W  S  C  T  Q  L",
+		"5  Pistolet 1.0  1.0  0  0  -  0  3  In_Battle",
+		"",
+		"Battle Protocol",
+		"",
+		"Bar  Pistolet  fires  on  Foo  Drone  :  Destroyed",
+		"Bar  Pistolet  fires  on  Foo  Drone  :  Destroyed",
+		"Bar  Pistolet  fires  on  Foo  Drone  :  Destroyed",
+		"Bar  Pistolet  fires  on  Foo  Drone  :  Destroyed",
+		"",
+	}, "\n")
+
+	rep, battles, err := Parse(strings.NewReader(in))
+	if err != nil {
+		t.Fatalf("Parse: %v", err)
+	}
+	if got, want := len(battles), 1; got != want {
+		t.Fatalf("len(battles) = %d, want %d", got, want)
+	}
+	b := battles[0]
+
+	// The three Foo roster rows collapse into two BattleReportGroup
+	// entries: one Foo:Drone (rows 1+2) and one Foo:Cruiser (row 3),
+	// plus one Bar:Pistolet. Total 3 groups, NOT 4.
+	if got, want := len(b.Ships), 3; got != want {
+		t.Fatalf("battle.Ships = %d groups, want %d (duplicate class rows must merge)", got, want)
+	}
+
+	var drone, cruiser, pistolet *report.BattleReportGroup
+	for i := range b.Ships {
+		g := b.Ships[i]
+		switch g.ClassName {
+		case "Drone":
+			drone = &g
+		case "Cruiser":
+			cruiser = &g
+		case "Pistolet":
+			pistolet = &g
+		}
+	}
+	if drone == nil || cruiser == nil || pistolet == nil {
+		t.Fatalf("missing class: drone=%v cruiser=%v pistolet=%v", drone, cruiser, pistolet)
+	}
+
+	// Drone rows sum to Number = 3 + 4 = 7 and NumberLeft = 1 + 2 = 3.
+	// Protocol corroborates: four Destroyed shots against Drone, so
+	// 7 - 3 = 4 — the protocol's destroy count reconciles with the
+	// recorded delta only when both rows are summed.
+	if drone.Number != 7 {
+		t.Errorf("Drone.Number = %d, want 7 (3+4)", drone.Number)
+	}
+	if drone.NumberLeft != 3 {
+		t.Errorf("Drone.NumberLeft = %d, want 3 (1+2)", drone.NumberLeft)
+	}
+	// Cruiser and Pistolet are single-row classes — counts must match
+	// the file verbatim with no spurious merging across classes.
+	if cruiser.Number != 10 || cruiser.NumberLeft != 9 {
+		t.Errorf("Cruiser = (Number=%d, NumberLeft=%d), want (10, 9)",
+			cruiser.Number, cruiser.NumberLeft)
+	}
+	if pistolet.Number != 5 || pistolet.NumberLeft != 3 {
+		t.Errorf("Pistolet = (Number=%d, NumberLeft=%d), want (5, 3)",
+			pistolet.Number, pistolet.NumberLeft)
+	}
+
+	// rep-level summary must reflect the merged shape: 4 shots, one
+	// battle, no crash or spurious extra battles.
+	if got, want := len(rep.Battle), 1; got != want {
+		t.Fatalf("len(rep.Battle) = %d, want %d", got, want)
+	}
+	if rep.Battle[0].Shots != 4 {
+		t.Errorf("rep.Battle[0].Shots = %d, want 4", rep.Battle[0].Shots)
+	}
+}
+
 // TestParseYourGroups exercises the local-group section. Two rows
 // cover the on-planet ("In_Orbit", origin "-") and in-space ("In_Space",
 // origin name + range) variants, plus a cargo-loaded row to assert the