gofmt: bring internal/ and cmd/ back to gofmt -l clean

Mechanical `gofmt -w ./internal ./cmd`. Mostly struct-field realignment that
had drifted, plus a few trailing-newline fixes. No behaviour change — gofmt is
semantics-preserving, and build/vet/test are green either side.

Split out from the code-review fixes that follow so those stay reviewable
instead of hiding inside a wall of realignment.

internal/plugin/adventure_activities.go

@@ -642,7 +642,7 @@ type AdvActionResult struct {
 	FlavorKey      string
 	EquipBroken    []EquipmentSlot
 	NearDeath      bool
-	StreakBonus     int
+	StreakBonus    int
 	CombatLog      *CombatResult
 	// MasteryCrossings records equipment slots whose ActionsUsed crossed a
 	// mastery threshold (advMasteryThresholds) on this action. The caller