fix(plugins): install local plugins on packaged desktop

The plugin compiler spawned esbuild through app.asar, and the subprocess
imported the React client barrel. Point esbuild at the unpacked binary,
add a react-free @paseo/plugin/server entry, and pass a typed PluginTheme
so plugin UI follows the active theme on desktop and mobile.

plugin-examples/linear/issues.shared.ts

@@ -1,4 +1,4 @@
-import { defineAttachmentSource, defineRpc } from "@paseo/plugin";
+import { defineAttachmentSource, defineRpc } from "@paseo/plugin/server";
 import { z } from "zod";
 
 const SearchPayloadSchema = z.object({