Clean up repository structure and release docs

tests/core/PDFFileSelectionTests.swift

@@ -0,0 +1,24 @@
+import XCTest
+@testable import IHatePDFsCore
+
+final class PDFFileSelectionTests: XCTestCase {
+    func testPDFFileURLAcceptsPDFExtensionsCaseInsensitively() {
+        XCTAssertTrue(PDFFileSelection.isPDFFileURL(URL(fileURLWithPath: "/tmp/article.pdf")))
+        XCTAssertTrue(PDFFileSelection.isPDFFileURL(URL(fileURLWithPath: "/tmp/article.PDF")))
+    }
+
+    func testPDFFileURLRejectsNonPDFAndRemoteURLs() {
+        XCTAssertFalse(PDFFileSelection.isPDFFileURL(URL(fileURLWithPath: "/tmp/notes.txt")))
+        XCTAssertFalse(PDFFileSelection.isPDFFileURL(URL(string: "https://example.com/article.pdf")!))
+    }
+
+    func testPDFFileURLRejectsDirectoriesNamedLikePDFs() throws {
+        let directory = FileManager.default.temporaryDirectory
+            .appendingPathComponent(UUID().uuidString)
+            .appendingPathExtension("pdf")
+        try FileManager.default.createDirectory(at: directory, withIntermediateDirectories: true)
+        defer { try? FileManager.default.removeItem(at: directory) }
+
+        XCTAssertFalse(PDFFileSelection.isPDFFileURL(directory))
+    }
+}