fix(electron-compat): prepend globalThis.Bun shim to prevent Electron/Node crash

On Node/Electron, globalThis.Bun is undefined. The Bun bundler emits top-level
  var { spawn } = globalThis.Bun;
destructures from its internal modules, causing 'Cannot destructure property
of undefined' before any plugin hook is reached (25 occurrences in dist/index.js).

Fix:
- Add src/electron-compat.ts: a side-effect module that populates globalThis.Bun
  with node:child_process-backed spawn/spawnSync shims when Bun is unavailable
- Add script/prepend-electron-shim.ts: post-build script that prepends the shim
  code to dist/index.js, guaranteeing it runs BEFORE the top-level destructures
  (Bun bundler does not preserve import side-effect evaluation order reliably)
- Update build script to run prepend-shim after bundling
- Add src/electron-compat.test.ts verifying shim position in dist

The shim only activates when globalThis.Bun is absent (real Bun runtime is
unaffected). Spawn-dependent features degrade gracefully at call time.

Fixes #3797 (follow-up to #3795/#3796)

src/electron-compat.test.ts

@@ -0,0 +1,27 @@
+import { describe, test, expect } from "bun:test"
+
+describe("electron-compat shim", () => {
+  test("#given shim module #when inspected #then it exports no values (side-effect only)", async () => {
+    // The shim is a side-effect module — no named exports
+    const mod = await import("./electron-compat")
+    expect(Object.keys(mod)).toHaveLength(0)
+  })
+
+  test("#given Bun runtime #when shim is loaded #then globalThis.Bun remains the real Bun", () => {
+    // In Bun (our test environment), globalThis.Bun is already defined.
+    // The shim must not overwrite it.
+    expect(globalThis.Bun).toBeDefined()
+    // Real Bun version looks like "1.x.x", not our shim string
+    expect(globalThis.Bun.version).not.toBe("0.0.0-node-shim")
+  })
+
+  test("#given dist/index.js #when inspected #then compat shim appears before first globalThis.Bun destructure", async () => {
+    // This test guards that build/prepend-electron-shim ran.
+    // If the shim is missing, the plugin crashes on Electron at line 2876.
+    const dist = await Bun.file("dist/index.js").text()
+    const shimPos = dist.indexOf("[omo] Electron/Node compat shim")
+    const firstDestructure = dist.indexOf("} = globalThis.Bun;")
+    expect(shimPos).toBeGreaterThanOrEqual(0) // shim present
+    expect(shimPos).toBeLessThan(firstDestructure) // shim before destructures
+  })
+})

src/electron-compat.ts

@@ -0,0 +1,74 @@
+/**
+ * Electron/Node runtime compatibility shim.
+ *
+ * OpenCode Desktop runs the plugin in an Electron renderer/main process
+ * whose ESM loader is Node — not Bun. When bundled with `--target bun`,
+ * every chunk that calls `Bun.spawn` / `Bun.spawnSync` emits a top-level
+ * `var { spawn } = globalThis.Bun` destructure. On Node/Electron,
+ * `globalThis.Bun` is `undefined`, so module evaluation crashes before any
+ * plugin hook is ever reached.
+ *
+ * We patch globalThis.Bun at module-evaluation time so the destructures
+ * resolve to real functions backed by node:child_process.
+ */
+
+// eslint-disable-next-line @typescript-eslint/no-require-imports
+const _cp = require("node:child_process") as typeof import("node:child_process")
+// eslint-disable-next-line @typescript-eslint/no-require-imports
+const _stream = require("node:stream") as typeof import("node:stream")
+
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+type AnyRecord = Record<string, any>
+
+function _makeProc(proc: ReturnType<typeof _cp.spawn>) {
+  let _exitCode: number | null = null
+  const exited = new Promise<number>((resolve) => {
+    proc.on("exit", (code) => { _exitCode = code ?? 1; resolve(_exitCode) })
+    proc.on("error", () => { if (_exitCode === null) { _exitCode = 1; resolve(1) } })
+  })
+  return {
+    get exitCode() { return _exitCode },
+    exited,
+    stdout: proc.stdout ? (_stream.Readable.toWeb(proc.stdout) as ReadableStream<Uint8Array>) : undefined,
+    stderr: proc.stderr ? (_stream.Readable.toWeb(proc.stderr) as ReadableStream<Uint8Array>) : undefined,
+    stdin: proc.stdin,
+    kill(sig?: NodeJS.Signals) { try { proc.kill(sig) } catch {} },
+    pid: proc.pid,
+  }
+}
+
+function _spawnShim(cmdOrOpts: string[] | AnyRecord, optsArg?: AnyRecord) {
+  const isObj = !Array.isArray(cmdOrOpts)
+  const cmd: string[] = isObj ? (cmdOrOpts as AnyRecord)["cmd"] as string[] : (cmdOrOpts as string[])
+  const o: AnyRecord = isObj ? (cmdOrOpts as AnyRecord) : (optsArg ?? {})
+  const [bin, ...args] = cmd
+  const proc = _cp.spawn(bin, args, {
+    cwd: o["cwd"] as string | undefined,
+    env: o["env"] as NodeJS.ProcessEnv | undefined,
+    stdio: [(o["stdin"] ?? "pipe") as "pipe", (o["stdout"] ?? "pipe") as "pipe", (o["stderr"] ?? "pipe") as "pipe"],
+  })
+  return _makeProc(proc)
+}
+
+function _spawnSyncShim(cmdOrOpts: string[] | AnyRecord) {
+  const isObj = !Array.isArray(cmdOrOpts)
+  const cmd: string[] = isObj ? (cmdOrOpts as AnyRecord)["cmd"] as string[] : (cmdOrOpts as string[])
+  const o: AnyRecord = isObj ? (cmdOrOpts as AnyRecord) : {}
+  const [bin, ...args] = cmd
+  const r = _cp.spawnSync(bin, args, {
+    cwd: o["cwd"] as string | undefined,
+    env: o["env"] as NodeJS.ProcessEnv | undefined,
+    stdio: ["pipe", "pipe", "pipe"],
+  })
+  return { exitCode: r.status ?? 1, stdout: r.stdout, stderr: r.stderr }
+}
+
+if (!globalThis.Bun) {
+  // @ts-expect-error – intentional globalThis shim for Electron/Node compat
+  globalThis.Bun = {
+    spawn: _spawnShim as unknown as typeof globalThis.Bun.spawn,
+    spawnSync: _spawnSyncShim as unknown as typeof globalThis.Bun.spawnSync,
+    env: process.env,
+    version: "0.0.0-node-shim",
+  }
+}

src/index.ts

@@ -1,3 +1,4 @@
+import "./electron-compat"
 import { initConfigContext } from "./cli/config-manager/config-context"
 import type { Hooks, Plugin, PluginModule } from "@opencode-ai/plugin"