feat(typing): add English autocomplete and Chinese candidate expand panel

Offline English lexicon suggestions with autocapitalization, plus a same-height Chinese more-candidates grid over the key area.

OSGKeyboardShared/Typing/EnglishLearningStore.swift

@@ -0,0 +1,45 @@
+// EnglishLearningStore.swift
+// OSGKeyboard · Shared
+//
+// Lightweight per-word boost counts for English typing. Lives in the App
+// Group so the extension can read/write without touching PersonalDictionary.
+
+import Foundation
+
+/// Records accepted suggestions / defended originals for ranking.
+public final class EnglishLearningStore: @unchecked Sendable {
+    public static let defaultsKey = "englishTyping.learnedBoosts.v1"
+
+    private let defaults: UserDefaults
+
+    public init(defaults: UserDefaults = AppGroupStore().defaults) {
+        self.defaults = defaults
+    }
+
+    public func boost(for word: String) -> Int {
+        let key = word.lowercased()
+        guard !key.isEmpty else { return 0 }
+        return snapshot()[key] ?? 0
+    }
+
+    public func recordAcceptance(of word: String, amount: Int = 3) {
+        mutate(word: word, delta: amount)
+    }
+
+    public func recordDefense(of word: String, amount: Int = 5) {
+        // User rejected autocorrect / insisted on original spelling.
+        mutate(word: word, delta: amount)
+    }
+
+    public func snapshot() -> [String: Int] {
+        (defaults.dictionary(forKey: Self.defaultsKey) as? [String: Int]) ?? [:]
+    }
+
+    private func mutate(word: String, delta: Int) {
+        let key = word.lowercased()
+        guard !key.isEmpty else { return }
+        var map = snapshot()
+        map[key] = min(10_000, (map[key] ?? 0) + delta)
+        defaults.set(map, forKey: Self.defaultsKey)
+    }
+}