fix: resolve all linting errors and add SSE compression

- Add brotli compression (level 5) to long-lived SSE event streams
  (HandleGameEvents, HandleSnakeEvents) to reduce wire payload
- Fix all errcheck violations with nolint annotations for best-effort calls
- Fix goimports: separate stdlib, third-party, and local import groups
- Fix staticcheck: add package comments, use tagged switch
- Zero lint issues remaining

features/c4game/handlers.go

@@ -12,11 +12,12 @@ import (
 	"github.com/alexedwards/scs/v2"
 	"github.com/go-chi/chi/v5"
 	"github.com/nats-io/nats.go"
+	"github.com/starfederation/datastar-go/datastar"
+
 	"github.com/ryanhamamura/c4/db/repository"
 	"github.com/ryanhamamura/c4/features/c4game/components"
 	"github.com/ryanhamamura/c4/features/c4game/pages"
 	"github.com/ryanhamamura/c4/game"
-	"github.com/starfederation/datastar-go/datastar"
 )
 
 func HandleGamePage(store *game.GameStore, sessions *scs.SessionManager, queries *repository.Queries) http.HandlerFunc {
@@ -102,7 +103,9 @@ func HandleGameEvents(store *game.GameStore, nc *nats.Conn, sessions *scs.Sessio
 
 		myColor := gi.GetPlayerColor(playerID)
 
-		sse := datastar.NewSSE(w, r)
+		sse := datastar.NewSSE(w, r, datastar.WithCompression(
+			datastar.WithBrotli(datastar.WithBrotliLevel(5)),
+		))
 
 		// Load initial chat messages
 		chatMsgs := loadChatMessages(queries, gameID)
@@ -118,7 +121,7 @@ func HandleGameEvents(store *game.GameStore, nc *nats.Conn, sessions *scs.Sessio
 		if err != nil {
 			return
 		}
-		defer gameSub.Unsubscribe()
+		defer gameSub.Unsubscribe() //nolint:errcheck
 
 		// Subscribe to chat messages
 		chatCh := make(chan *nats.Msg, 64)
@@ -126,7 +129,7 @@ func HandleGameEvents(store *game.GameStore, nc *nats.Conn, sessions *scs.Sessio
 		if err != nil {
 			return
 		}
-		defer chatSub.Unsubscribe()
+		defer chatSub.Unsubscribe() //nolint:errcheck
 
 		ctx := r.Context()
 		for {
@@ -263,7 +266,7 @@ func HandleSendChat(store *game.GameStore, nc *nats.Conn, sessions *scs.SessionM
 			datastar.NewSSE(w, r)
 			return
 		}
-		nc.Publish("game.chat."+gameID, data)
+		nc.Publish("game.chat."+gameID, data) //nolint:errcheck
 
 		// Clear the chat input
 		sse := datastar.NewSSE(w, r)