feat: add Command-number launch hints and Finder icon

Sources/ConjureKit/CommandNumberShortcuts.swift

@@ -0,0 +1,34 @@
+import Foundation
+
+/// Monotonic timestamps are supplied by the window; tests never wait on a real clock.
+public struct CommandNumberShortcuts: Sendable {
+    private var heldSince: TimeInterval?
+    public private(set) var isVisible = false
+
+    public init() {}
+
+    /// Returns true only when a fresh, eligible Command-only hold begins.
+    public mutating func update(commandOnly: Bool, eligible: Bool, at time: TimeInterval) -> Bool {
+        guard commandOnly && eligible else { reset(); return false }
+        guard heldSince == nil else { return false }
+        heldSince = time
+        return true
+    }
+
+    public mutating func reveal(at time: TimeInterval) -> Bool {
+        guard let heldSince, time - heldSince >= 1 else { return false }
+        isVisible = true
+        return true
+    }
+
+    public func index(for key: String) -> Int? {
+        guard isVisible, key.utf8.count == 1, let digit = key.utf8.first,
+              (49...57).contains(digit) else { return nil }
+        return Int(digit - 49)
+    }
+
+    public mutating func reset() {
+        heldSince = nil
+        isVisible = false
+    }
+}