Key-file picker in the connection manager

Choose... button beside the private-key field opens the native file dialog
starting in ~/.ssh (Utils.openFileDialog via a pickKeyFile RPC).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/bun/rpc-handlers.ts

@@ -203,6 +203,20 @@ export function createAppRPC({
 						return { path };
 					}),
 
+				pickKeyFile: () =>
+					wrap(async () => {
+						const { homedir } = await import("node:os");
+						const picked = await Utils.openFileDialog({
+							startingFolder: `${homedir()}/.ssh`,
+							allowedFileTypes: "*",
+							canChooseFiles: true,
+							canChooseDirectory: false,
+							allowsMultipleSelection: false,
+						});
+						const path = picked.find((p) => p.trim().length > 0) ?? null;
+						return { path };
+					}),
+
 				getEditLeftovers: () =>
 					wrap(async () => ({ names: await edits.listLeftovers() })),