clide:// deep link handler — open files at a line (T-56)

clide://open?path=&line= translates (in parseArgv) to editor.open, so an OS
scheme invocation routes through the existing CLI→IPC path into the running
window — single-instance for free, no new code path. Registered the scheme:
linux/clide.desktop MimeType x-scheme-handler/clide (Exec already passes %U) and
macOS Info.plist CFBundleURLTypes. Parser validates the action/path/line.

Linux works end to end (the OS passes the URL as argv). macOS URL DELIVERY (the
AppDelegate openURLs callback → forward into this path) is a follow-up — the
scheme is registered, but the native hook needs a real macOS machine to verify,
so it's not shipped blind. Also drops a stray import in clide_markdown_test.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

macos/Runner/Info.plist

@@ -28,5 +28,16 @@
 	<string>MainMenu</string>
 	<key>NSPrincipalClass</key>
 	<string>NSApplication</string>
+	<key>CFBundleURLTypes</key>
+	<array>
+		<dict>
+			<key>CFBundleURLName</key>
+			<string>net.schweitz.clide.deeplink</string>
+			<key>CFBundleURLSchemes</key>
+			<array>
+				<string>clide</string>
+			</array>
+		</dict>
+	</array>
 </dict>
 </plist>