feat: macOS architecture, cloud ASR/LLM providers, and 6-step iOS onboarding

- Add macOS menu-bar dictation app with local ASR models (SenseVoice/Qwen3),
  global Option hotkey, and bottom overlay
- Add cloud ASR/LLM providers (Anthropic, Volcengine, Bailian, and more) with
  provider logos, model listing, and connection checks
- Add shared 7-day usage stats UI (UsageStatsCluster / SevenDayUsageChart)
- Add iOS onboarding step 6 for polish LLM setup; hide custom-language-model
  diagnostic toggle behind DEBUG
- Unify iOS onboarding tagline with the macOS brand line ("开口即文字。")
- Rewrite README (Chinese-first, product-oriented) and refresh GitHub Pages

OSGKeyboardShared/Models/HandednessPreference.swift

@@ -2,7 +2,7 @@
 // OSGKeyboard · Shared
 //
 // Which hand the user holds the phone with — controls bottom-row key order
-// on the keyboard (delete ↔ return swap for right-handed use).
+// on the keyboard (delete ↔ space swap for right-handed use).
 
 import Foundation
 
@@ -19,7 +19,7 @@ public enum HandednessPreference: String, CaseIterable, Identifiable, Sendable,
         }
     }
 
-    /// Right-handed preference places return on the left and delete on the right.
+    /// Right-handed preference places space on the left and delete on the right.
     public var swapsActionKeys: Bool { self == .right }
 
     public static func fromStored(_ raw: String?) -> HandednessPreference {