fix(generator): drop incorrect distinctness assert in TestPlanetRandomName

`RandomName` builds the suffix as two independent `rand.Intn(1000)`
calls, so the two 4-digit halves collide on ~0.1% of runs. The
sub-test asserted `g[2] != g[3]`, which flakes whenever the same
value lands twice — once per ~1000 sub-runs per class, so across
the seven `PlanetClass` rows the integration suite hit it on
`#199 go-unit.yaml` against `feature/subscribe-events-heartbeat`
(`"0074"` collision).

Distinctness is not a property `RandomName` promises and is not
load-bearing for callers: `game/internal/controller/generate_game.go`
uses these names for planet labels and already tolerates duplicate
names across planets, so collisions inside one name are no worse
than collisions between names. Drop the assert; keep the format and
class-prefix checks, which are the actual contract.

Stress-tested with `-count=200`: 200 consecutive iterations × 7
classes = 1400 sub-runs without a single failure where the prior
version's flake probability would have surfaced ~once on average.

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

game/internal/generator/planet_test.go

@@ -18,14 +18,21 @@ func TestPlanetRandomName(t *testing.T) {
 	for _, pc := range []g.PlanetClass{g.PlanetClassHW, g.PlanetClassDW, g.PlanetClassGiant, g.PlanetClassBig, g.PlanetClassNormal, g.PlanetClassRich, g.PlanetClassAsterioid} {
 		t.Run(string(pc), func(t *testing.T) {
 			name := g.NewPlanet(pc, g.Coordinate{0, 0}, 0, 0).RandomName()
-			g := re.FindStringSubmatch(name)
-			assert.NotNilf(t, g, "cannot parse: %q", name)
-			if g == nil {
+			// `RandomName` formats `<class>-<4-digit>-<4-digit>`,
+			// where each suffix is an independent `rand.Intn(1000)`.
+			// We assert the wire format and the class prefix; an
+			// earlier revision also asserted `g[2] != g[3]`, which
+			// flaked on the legitimate ~0.1% collision (a property
+			// the function does not — and need not — guarantee:
+			// `generate_game.go` already tolerates duplicate names
+			// across planets).
+			groups := re.FindStringSubmatch(name)
+			assert.NotNilf(t, groups, "cannot parse: %q", name)
+			if groups == nil {
 				return
 			}
-			assert.Equalf(t, 4, len(g), "regexp groups")
-			assert.Equal(t, string(pc), g[1])
-			assert.NotEqual(t, g[2], g[3])
+			assert.Equalf(t, 4, len(groups), "regexp groups")
+			assert.Equal(t, string(pc), groups[1])
 		})
 	}
 }