Fix the keyboard typing pipeline + add a test that catches the regression

The earlier UIKeyInput conformance was declared in a separate extension. ObjC
protocol conformance via Swift extension is fragile when the protocol
inherits another @objc protocol (UIKeyInput inherits UITextInputTraits) — the
runtime didn't always pick up insertText:, so the on-screen keyboard came
up but characters never reached controller.type(_:).

Fix: declare UIKeyInput conformance directly on FramebufferUIView's class
declaration, with insertText / deleteBackward / hasText as native members.

Also caught and fixed by the new UI test:
- The toolbar's keyboard-icon button had a 20×13 hit region (SF Symbol size)
  even though the visual frame was 34×34 — XCUI taps couldn't land on it
  reliably. .contentShape(Rectangle()) widens the hit area to the frame.
- accessibilityValue is reserved by iOS for UIKeyInput-classed views (treats
  them as TextView), so a separate hidden "fb-diag" accessibility probe
  records keyboard plumbing events for the test to verify.

Tests:
- KeyboardInputTests (5): pure mapping from String → X11 keysym down/up pairs
- ScreensUITests.testSoftwareKeyboardSendsCharactersToFramebuffer:
  opens a session, taps the keyboard toggle, types "hi" via the system
  keyboard, and asserts the framebuffer's diagnostic probe records
  [ins:h] and [ins:i] — proving the chars reach controller.type(_:)
- A SwiftUI state probe (sessionview-state) verifies the binding flips,
  which guards against future tap-routing regressions.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Packages/VNCCore/Sources/VNCCore/Session/SessionController.swift

@@ -159,16 +159,50 @@ public final class SessionController {
 
     public func type(_ string: String) {
         guard !viewOnly else { return }
+        let events = Self.keyEvents(for: string)
+        recordTypedEvents(events)
+        guard let connection else { return }
+        for event in events {
+            let code = VNCKeyCode(event.keysym)
+            if event.isDown {
+                connection.keyDown(code)
+            } else {
+                connection.keyUp(code)
+            }
+        }
+    }
+
+    /// Pure mapping from a string to the key down/up keysym pairs it should
+    /// generate. Newlines map to X11 Return; all other printable ASCII maps
+    /// 1:1 to the equivalent X11 keysym (which equals the ASCII code).
+    public nonisolated static func keyEvents(for string: String) -> [KeyEvent] {
+        var events: [KeyEvent] = []
         for char in string {
             if char.isNewline {
-                pressKey(.return)
+                events.append(KeyEvent(keysym: 0xFF0D, isDown: true))
+                events.append(KeyEvent(keysym: 0xFF0D, isDown: false))
                 continue
             }
             for code in VNCKeyCode.withCharacter(char) {
-                connection?.keyDown(code)
-                connection?.keyUp(code)
+                events.append(KeyEvent(keysym: code.rawValue, isDown: true))
+                events.append(KeyEvent(keysym: code.rawValue, isDown: false))
             }
         }
+        return events
+    }
+
+    public struct KeyEvent: Equatable, Sendable {
+        public let keysym: UInt32
+        public let isDown: Bool
+    }
+
+    /// Test hook: when set, every typed event is appended here in addition to
+    /// being sent over the wire. Used by UI tests to verify keyboard plumbing.
+    public var typedEventLog: [KeyEvent] = []
+    public var typedEventLogEnabled: Bool = false
+    private func recordTypedEvents(_ events: [KeyEvent]) {
+        guard typedEventLogEnabled else { return }
+        typedEventLog.append(contentsOf: events)
     }
 
     public func sendBackspace() { pressKey(.delete) }