Fix spelling typos and improve code quality (#2186)

## Description:
  This PR fixes several bugs and improves code quality:

- Fix spelling typos: "recieved" → "received" in Transport.ts and
GameServer.ts
  - Fix comment typo: "isn'te" → "isn't" in TerrainLayer.ts
- Improve WebSocket cleanup in Transport.ts leaveGame() by replacing
empty onclose handler with proper
   killExistingSocket() call
- Add console.warn for image decode failures in StructureLayer.ts
instead of silent catch
  - Remove commented dead code in DevConfig.ts

  ## Testing
All 288 tests pass. Development build completes successfully. No
breaking changes.

  ## Files Changed
  - src/client/Transport.ts
  - src/server/GameServer.ts
  - src/client/graphics/layers/TerrainLayer.ts
  - src/client/graphics/layers/StructureLayer.ts
  - src/core/configuration/DevConfig.ts

## Checklist:
- [x] I have added screenshots for all UI updates (N/A - no UI changes)
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file (N/A - no user-facing text)
- [x] I have added relevant tests to the test directory (All 288
existing tests pass - no new tests needed for typo fixes)
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced

  Discord: hiphex_33496

Hiphex

Co-authored-by: Claude <noreply@anthropic.com>

src/core/configuration/DevConfig.ts

@@ -58,11 +58,6 @@ export class DevConfig extends DefaultConfig {
     super(sc, gc, us, isReplay);
   }
 
-  // numSpawnPhaseTurns(): number {
-  //   return this.gameConfig().gameType == GameType.Singleplayer ? 70 : 100;
-  //   // return 100
-  // }
-
   unitInfo(type: UnitType): UnitInfo {
     const info = super.unitInfo(type);
     // eslint-disable-next-line @typescript-eslint/no-unused-vars