feat: add package scaffold and DictationController state machine

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

Sources/SstCore/Models.swift

@@ -0,0 +1,35 @@
+import Foundation
+
+public enum HotkeyEvent: Equatable, Sendable {
+    case pressed
+    case released
+}
+
+public enum DictationState: Equatable, Sendable {
+    case idle
+    case recording
+    case transcribing
+    case inserting
+}
+
+public struct CleaningContext: Sendable {
+    public init() {}
+}
+
+public protocol AudioRecording {
+    func start() throws
+    /// Stops recording and returns all captured 16 kHz mono Float samples.
+    func stop() -> [Float]
+}
+
+public protocol Transcriber {
+    func transcribe(_ samples: [Float]) async throws -> String
+}
+
+public protocol Cleaner {
+    func clean(_ text: String, context: CleaningContext) async throws -> String
+}
+
+public protocol TextInserting {
+    func insert(_ text: String) async throws
+}