Add real oAITests target; remove disconnected SPM test scaffold

The old Tests/oAITests/oAITests.swift + root Package.swift/Sources/
were a swift package init stub that @testable imported a fake empty
oAI module, completely disconnected from the real ~31K-line app
(built only via oAI.xcodeproj). Running `swift test` there would
have silently "passed" while testing nothing.

oAITests is a proper Unit Testing Bundle target added via Xcode's
target editor, wired into the app's scheme (TestAction references
oAITests.xctest). Verified with `xcodebuild test` before and after
removing the dead scaffold.

First phase of the test-suite rollout plan (peaceful-baking-kurzweil).

oAITests/oAITests.swift

@@ -0,0 +1,18 @@
+//
+//  oAITests.swift
+//  oAITests
+//
+//  Created by Rune Olsen on 23/07/2026.
+//
+
+import Testing
+
+struct oAITests {
+
+    @Test func example() async throws {
+        // Write your test here and use APIs like `#expect(...)` to check expected conditions.
+        // Swift Testing Documentation
+        // https://developer.apple.com/documentation/testing
+    }
+
+}