feat(keyboard): add Notes skill and system-style typing

Add save-to-Notes export and direct map handoff while aligning multi-touch typing, period shortcuts, return actions, and navigation visuals with system behavior.

OSGKeyboardShared/Typing/PeriodShortcut.swift

@@ -0,0 +1,28 @@
+// PeriodShortcut.swift
+// OSGKeyboard · Shared
+//
+// iOS "." Shortcut: a second Space shortly after a Space that follows a
+// word character becomes ". " and arms sentence Shift.
+
+import Foundation
+
+public enum PeriodShortcut: Sendable {
+    /// Window for the second Space tap. Slow consecutive spaces stay spaces.
+    public static let doubleTapInterval: TimeInterval = 0.45
+
+    /// Whether `precedingText` (already including the first space) can take
+    /// the shortcut: `…X ` where X is a letter or number, not a terminator.
+    public static func shouldReplacePreviousSpace(precedingText: String) -> Bool {
+        guard precedingText.last == " " else { return false }
+        guard let previous = precedingText.dropLast().last else { return false }
+        if previous.isWhitespace || previous.isNewline { return false }
+        return previous.isLetter || previous.isNumber
+    }
+
+    /// After inserting a space, arm only when that space followed a word char.
+    public static func shouldArm(afterSpaceFollowing precedingBeforeSpace: String) -> Bool {
+        guard let last = precedingBeforeSpace.last else { return false }
+        if last.isWhitespace || last.isNewline { return false }
+        return last.isLetter || last.isNumber
+    }
+}