fix(bun-spawn-shim): eliminate globalThis.Bun top-level destructures for Electron/Node compat

Root cause: bun build --target bun inlines top-level
  var { spawn } = globalThis.Bun;
for every file that contains 'import { spawn } from "bun"'. On Node/Electron
where globalThis.Bun is undefined, this crashes with
  Cannot destructure property 'spawn' of 'globalThis.Bun' as it is undefined.
26 source files had this import; the bundled output had 25 top-level destructures.

Fix:
- Add src/shared/bun-spawn-shim.ts: a thin wrapper that
  - delegates to Bun.spawn/spawnSync when globalThis.Bun is present (real Bun)
  - falls back to static ESM imports of node:child_process otherwise
  - uses static 'import { spawn } from "node:child_process"' so Bun bundler
    does NOT emit any globalThis.Bun destructures for this module
- Replace all 26 'from "bun"' spawn/spawnSync imports with relative paths to shim
- Replace 4 direct Bun.spawn() call sites with shim's spawn()
- Remove src/electron-compat.ts and script/prepend-electron-shim.ts (no longer needed)
- Update src/electron-compat.test.ts to assert 0 top-level globalThis.Bun destructures

Verification: grep -c '} = globalThis.Bun;' dist/index.js → 0 (was 25)
All 5921 tests pass (1 pre-existing timeout failure unrelated to this change).

Fixes #3797

src/shared/binary-downloader.ts

@@ -1,6 +1,6 @@
 import { chmodSync, existsSync, mkdirSync, unlinkSync } from "node:fs";
 import * as path from "node:path";
-import { spawn } from "bun";
+import { spawn } from "./bun-spawn-shim";
 import { validateArchiveEntries, type ArchiveEntry } from "./archive-entry-validator";
 import { extractZip } from "./zip-extractor";
 

src/shared/bun-spawn-shim.ts

@@ -0,0 +1,68 @@
+/**
+ * Node/Electron-compatible spawn shim.
+ *
+ * Replaces direct `import { spawn } from "bun"` throughout the codebase so
+ * that `bun build --target bun` no longer emits top-level
+ *   var { spawn } = globalThis.Bun;
+ * destructures that crash on Node/Electron (where globalThis.Bun is undefined).
+ *
+ * On real Bun runtime:  delegates straight to Bun.spawn / Bun.spawnSync.
+ * On Node/Electron:     backed by node:child_process (via static ESM imports
+ *                       which are safe in both runtimes).
+ */
+
+/* eslint-disable @typescript-eslint/no-explicit-any */
+
+import { spawn as nodeSpawn, spawnSync as nodeSpawnSync } from "node:child_process"
+import { Readable } from "node:stream"
+
+const IS_BUN = typeof globalThis.Bun !== "undefined"
+
+function _resolveCmd(cmdOrOpts: any, optsArg?: any): { cmd: string[]; opts: any } {
+  const isObj = !Array.isArray(cmdOrOpts)
+  return {
+    cmd: isObj ? (cmdOrOpts as any).cmd : (cmdOrOpts as string[]),
+    opts: isObj ? cmdOrOpts : (optsArg ?? {}),
+  }
+}
+
+function _wrapNodeProc(proc: ReturnType<typeof nodeSpawn>): any {
+  let code: number | null = null
+  const exited = new Promise<number>((resolve) => {
+    proc.on("exit", (c) => { code = c ?? 1; resolve(code) })
+    proc.on("error", () => { if (code === null) { code = 1; resolve(1) } })
+  })
+  return {
+    get exitCode() { return code },
+    exited,
+    stdout: proc.stdout ? Readable.toWeb(proc.stdout) as ReadableStream<Uint8Array> : undefined,
+    stderr: proc.stderr ? Readable.toWeb(proc.stderr) as ReadableStream<Uint8Array> : undefined,
+    stdin: proc.stdin,
+    kill(s?: NodeJS.Signals) { try { proc.kill(s) } catch {} },
+    pid: proc.pid,
+  }
+}
+
+export function spawn(cmdOrOpts: any, opts?: any): any {
+  if (IS_BUN) return (globalThis.Bun as any).spawn(cmdOrOpts, opts)
+  const { cmd, opts: o } = _resolveCmd(cmdOrOpts, opts)
+  const [bin, ...args] = cmd
+  const proc = nodeSpawn(bin, args, {
+    cwd: o.cwd as string | undefined,
+    env: o.env as NodeJS.ProcessEnv | undefined,
+    stdio: [(o.stdin ?? "pipe") as any, (o.stdout ?? "pipe") as any, (o.stderr ?? "pipe") as any],
+  })
+  return _wrapNodeProc(proc)
+}
+
+export function spawnSync(cmdOrOpts: any, _opts?: any): any {
+  if (IS_BUN) return (globalThis.Bun as any).spawnSync(cmdOrOpts)
+  const { cmd, opts: o } = _resolveCmd(cmdOrOpts)
+  const [bin, ...args] = cmd
+  const r = nodeSpawnSync(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, success: (r.status ?? 1) === 0, pid: -1 }
+}

src/shared/spawn-with-windows-hide.ts

@@ -1,4 +1,4 @@
-import { spawn as bunSpawn } from "bun"
+import { spawn as bunSpawn } from "./bun-spawn-shim"
 import { spawn as nodeSpawn, type ChildProcess } from "node:child_process"
 import { Readable } from "node:stream"
 

src/shared/tmux/tmux-utils/layout.ts

@@ -1,4 +1,4 @@
-import { spawn } from "bun"
+import { spawn } from "../../bun-spawn-shim"
 import type { TmuxLayout } from "../../../config/schema"
 import { getTmuxPath } from "../../../tools/interactive-bash/tmux-path-resolver"
 

src/shared/tmux/tmux-utils/pane-dimensions.ts

@@ -1,4 +1,4 @@
-import { spawn } from "bun"
+import { spawn } from "../../bun-spawn-shim"
 import { getTmuxPath } from "../../../tools/interactive-bash/tmux-path-resolver"
 
 export interface PaneDimensions {

src/shared/tmux/tmux-utils/pane-replace.ts

@@ -1,4 +1,4 @@
-import { spawn } from "bun"
+import { spawn } from "../../bun-spawn-shim"
 import type { TmuxConfig } from "../../../config/schema"
 import { getTmuxPath } from "../../../tools/interactive-bash/tmux-path-resolver"
 import type { SpawnPaneResult } from "../types"

src/shared/tmux/tmux-utils/pane-spawn.ts

@@ -1,4 +1,4 @@
-import { spawn } from "bun"
+import { spawn } from "../../bun-spawn-shim"
 import type { TmuxConfig } from "../../../config/schema"
 import { getTmuxPath } from "../../../tools/interactive-bash/tmux-path-resolver"
 import type { SpawnPaneResult } from "../types"

src/shared/tmux/tmux-utils/session-spawn.ts

@@ -1,4 +1,4 @@
-import { spawn } from "bun"
+import { spawn } from "../../bun-spawn-shim"
 import type { TmuxConfig } from "../../../config/schema"
 import { getTmuxPath } from "../../../tools/interactive-bash/tmux-path-resolver"
 import type { SpawnPaneResult } from "../types"

src/shared/tmux/tmux-utils/spawn-process.ts

@@ -1 +1 @@
-export { spawn } from "bun"
+export { spawn } from "../../bun-spawn-shim"

src/shared/tmux/tmux-utils/window-spawn.ts

@@ -1,4 +1,4 @@
-import { spawn } from "bun"
+import { spawn } from "../../bun-spawn-shim"
 import type { TmuxConfig } from "../../../config/schema"
 import { getTmuxPath } from "../../../tools/interactive-bash/tmux-path-resolver"
 import type { SpawnPaneResult } from "../types"

src/shared/zip-entry-listing/powershell-zip-entry-listing.ts

@@ -1,4 +1,4 @@
-import { spawn } from "bun"
+import { spawn } from "../bun-spawn-shim"
 
 import type { ArchiveEntry } from "../archive-entry-validator"
 

src/shared/zip-entry-listing/python-zip-entry-listing.ts

@@ -1,4 +1,4 @@
-import { spawn, spawnSync } from "bun"
+import { spawn, spawnSync } from "../bun-spawn-shim"
 
 import type { ArchiveEntry } from "../archive-entry-validator"
 

src/shared/zip-entry-listing/read-zip-symlink-target.ts

@@ -1,4 +1,4 @@
-import { spawn } from "bun"
+import { spawn } from "../bun-spawn-shim"
 
 export async function readZipSymlinkTarget(
 	archivePath: string,

src/shared/zip-entry-listing/tar-zip-entry-listing.ts

@@ -1,4 +1,4 @@
-import { spawn } from "bun"
+import { spawn } from "../bun-spawn-shim"
 
 import type { ArchiveEntry } from "../archive-entry-validator"
 import { log } from "../logger"

src/shared/zip-entry-listing/zipinfo-zip-entry-listing.ts

@@ -1,4 +1,4 @@
-import { spawn, spawnSync } from "bun"
+import { spawn, spawnSync } from "../bun-spawn-shim"
 
 import type { ArchiveEntry } from "../archive-entry-validator"
 import { readZipSymlinkTarget } from "./read-zip-symlink-target"

src/shared/zip-extractor.ts

@@ -1,4 +1,4 @@
-import { spawn, spawnSync } from "bun"
+import { spawn, spawnSync } from "./bun-spawn-shim"
 import { release } from "os"
 
 import { validateArchiveEntries } from "./archive-entry-validator"