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>

ScreensUITests/ScreensUITests.swift

@@ -46,13 +46,11 @@ final class ScreensUITests: XCTestCase {
         search.typeText("mini")
         XCTAssertEqual(search.value as? String, "mini",
                        "Search text should round-trip")
-        // Title should still be visible (top chrome does not scroll off)
         XCTAssertTrue(title.isHittable, "Title should remain on screen during search")
 
         // ---- Empty-state CTA routes to Add Connection.
         let emptyCTA = app.buttons["Add a computer"]
         if emptyCTA.waitForExistence(timeout: 1) {
-            // clear search first
             app.buttons["Clear search"].tap()
             emptyCTA.tap()
             XCTAssertTrue(displayNameField.waitForExistence(timeout: 2),
@@ -60,4 +58,72 @@ final class ScreensUITests: XCTestCase {
             app.buttons["Cancel"].tap()
         }
     }
+
+    /// Adds a connection with an unreachable host so the SessionView opens
+    /// (controller exists, no real network needed) and verifies that tapping
+    /// the keyboard icon presents the iOS keyboard and that pressing keys
+    /// flows through the framebuffer view's input handling.
+    @MainActor
+    func testSoftwareKeyboardSendsCharactersToFramebuffer() {
+        let app = XCUIApplication()
+        app.launch()
+
+        // Add a bogus connection
+        app.buttons["Add connection"].tap()
+        let nameField = app.textFields["Display name"]
+        XCTAssertTrue(nameField.waitForExistence(timeout: 2))
+        nameField.tap()
+        nameField.typeText("KeyboardTest")
+        let hostField = app.textFields["Host or IP"]
+        hostField.tap()
+        hostField.typeText("127.0.0.1")
+        app.buttons["Add"].tap()
+
+        // Open the connection
+        app.buttons.matching(NSPredicate(format: "label CONTAINS[c] %@", "KeyboardTest")).firstMatch.tap()
+
+        // Framebuffer exists (as a TextView once UIKeyInput is adopted)
+        let framebuffer = app.descendants(matching: .any)
+            .matching(identifier: "framebuffer").firstMatch
+        XCTAssertTrue(framebuffer.waitForExistence(timeout: 5),
+                      "Framebuffer view should exist in session")
+
+        // The diagnostic probe is a hidden sibling element that records
+        // keyboard plumbing events via its accessibilityLabel.
+        let diag = app.descendants(matching: .any)
+            .matching(identifier: "fb-diag").firstMatch
+        XCTAssertTrue(diag.waitForExistence(timeout: 3),
+                      "Diagnostic probe should exist")
+
+        // State probe
+        let state = app.descendants(matching: .any)
+            .matching(identifier: "sessionview-state").firstMatch
+        XCTAssertTrue(state.waitForExistence(timeout: 3))
+        XCTAssertEqual(state.label, "kb=false", "Initial binding should be false")
+
+        // Tap the keyboard toggle in the toolbar
+        let kbToggle = app.buttons["Toggle keyboard bar"]
+        XCTAssertTrue(kbToggle.waitForExistence(timeout: 2))
+        kbToggle.tap()
+
+        // Verify the binding flipped
+        let flippedTrue = NSPredicate(format: "label == %@", "kb=true")
+        wait(for: [expectation(for: flippedTrue, evaluatedWith: state)], timeout: 3)
+
+        // Wait for the diagnostic to record that we asked for the keyboard.
+        // The framebuffer was already first responder (for hardware keys), so
+        // we hit the reload path rather than `became:true`, which is fine.
+        let askedForKeyboard = NSPredicate(format: "label CONTAINS %@", "[set:true]")
+        wait(for: [expectation(for: askedForKeyboard, evaluatedWith: diag)],
+             timeout: 3)
+
+        // Type into the active first responder. Works even when the simulator
+        // suppresses the on-screen keyboard via Connect Hardware Keyboard.
+        app.typeText("hi")
+
+        let typedH = NSPredicate(format: "label CONTAINS %@", "[ins:h]")
+        wait(for: [expectation(for: typedH, evaluatedWith: diag)], timeout: 3)
+        let typedI = NSPredicate(format: "label CONTAINS %@", "[ins:i]")
+        wait(for: [expectation(for: typedI, evaluatedWith: diag)], timeout: 3)
+    }
 }