feat(keyboard): rank pinyin by habit and persist user dictionaries

Erase dialect syllables before abbrev so wom prefers 我们, flush librime
on leave, and add a settings action to forget learned Chinese and English order.

OSGKeyboardShared/Typing/LibrimeEngine.swift

@@ -58,7 +58,8 @@ public final class LibrimeEngine: RimeEngineBridging {
 
     public func teardown() {
         bridge?.clearComposition()
-        bridge?.stopSession()
+        // Session destroy alone does not flush LevelDB user dictionaries.
+        bridge?.finalizeRuntime()
         bridge = nil
         composition = .empty
         isReady = false