fix(build): keep index.js source map aligned with the bootstrap banner (#33899)

The main bootstrap banner was prepended to index.js in generateBundle,
after Rolldown had already emitted index.js.map, so every main-process
crash trace decoded ~200 lines off. Emit it via Rolldown's output.postBanner
instead, which shifts the source map natively.

Co-authored-by: outof-place <contact@outofplace.space>

config/scripts/main-entry-facade.test.ts

@@ -28,6 +28,9 @@ it('keeps main code and asset paths working after a CLI build replaces its publi
       'import { writeFileSync } from "node:fs"; import { join } from "node:path"; import { getStatus } from "./controls"; import { createTracker } from "./tracker"; import { getBootLabel } from "./boot-label"; import("./late").then(({ readLabel }) => writeFileSync(join(__dirname, "result.json"), JSON.stringify({ status: getStatus(), tracker: createTracker(), directory: __dirname, label: getBootLabel(), lateLabel: readLabel() })))'
     )
     const options = electronViteConfig.main?.build?.rollupOptions
+    if (Array.isArray(options?.output)) {
+      throw new Error('Expected one main-process output')
+    }
     await build({
       configFile: false,
       root,
@@ -37,6 +40,8 @@ it('keeps main code and asset paths working after a CLI build replaces its publi
         minify: electronViteConfig.main?.build?.minify,
         rolldownOptions: {
           ...options,
+          // Plugins and the bootstrap banner guard the real main entry, not this fixture.
+          output: { ...options?.output, postBanner: undefined },
           plugins: [],
           input: { index: join(root, 'main.ts'), controls: join(root, 'controls.ts') }
         }

electron.vite.config.ts

@@ -2,7 +2,7 @@ import { markdownParserAliases } from './config/build-plugins/markdown-parser-ex
 import { createRequire } from 'node:module'
 import { resolve } from 'node:path'
 import { defineConfig, type UserConfig } from 'electron-vite'
-import type { Plugin } from 'vite'
+import type { Plugin, Rollup } from 'vite'
 import react from '@vitejs/plugin-react'
 import tailwindcss from '@tailwindcss/vite'
 import { createBootstrapFatalExitBanner } from './config/build-plugins/bootstrap-fatal-exit-banner'
@@ -180,25 +180,16 @@ function createStartupDiagnosticsBanner(chunkName: string): string {
 `
 }
 
-function createMainBootstrapPlugin() {
-  return {
-    name: 'orca-main-bootstrap',
-    generateBundle(_options, bundle) {
-      const mainChunk = bundle['index.js']
-      if (!mainChunk || mainChunk.type !== 'chunk') {
-        return
-      }
-      if (!mainChunk.moduleIds.some((id) => resolve(id) === MAIN_BUILD_ENTRY_POINTS.index)) {
-        throw new Error('Main startup must stay in index.js so __dirname resolves app assets')
-      }
-
-      // Source guards run after Rollup’s require prelude, too late to handle missing bootstrap dependencies.
-      mainChunk.code =
-        createBootstrapFatalExitBanner() +
-        createStartupDiagnosticsBanner(mainChunk.fileName) +
-        mainChunk.code
-    }
+// postBanner lands after minification and Rolldown shifts index.js.map past it, keeping crash traces on the right line.
+function createMainBootstrapPostBanner(chunk: Rollup.RenderedChunk): string {
+  if (chunk.fileName !== 'index.js') {
+    return ''
   }
+  if (!chunk.moduleIds.some((id) => resolve(id) === MAIN_BUILD_ENTRY_POINTS.index)) {
+    throw new Error('Main startup must stay in index.js so __dirname resolves app assets')
+  }
+  // Source guards run after Rollup’s require prelude, too late to handle missing bootstrap dependencies.
+  return createBootstrapFatalExitBanner() + createStartupDiagnosticsBanner(chunk.fileName)
 }
 
 // Dev-only unminified main bundle exposes function names in V8 profiles; releases and pnpm build never read this flag.
@@ -231,10 +222,10 @@ export const electronViteConfig: UserConfig = {
           charset: 'ascii',
           format: 'cjs',
           entryFileNames: '[name].js',
-          chunkFileNames: 'chunks/[name]-[hash].js'
+          chunkFileNames: 'chunks/[name]-[hash].js',
+          postBanner: createMainBootstrapPostBanner
         },
         plugins: [
-          createMainBootstrapPlugin(),
           createPlainNodeEntryGuardPlugin(),
           createProcessHostDevRebuildPlugin(),
           createDarkBuildMarkerPlugin()