feat: self-heal Electron installs before dev and postinstall

Adds an Electron install check that repairs incomplete or wrong-architecture binaries
Runs the check during root postinstall and before electron dev startup
Adds tests and docs for the new ensure:electron workflow

packages/electron/package.json

@@ -31,6 +31,7 @@
     "dev": "node ./scripts/electron-dev.mjs",
     "build:web-assets": "node ./scripts/build-web-assets.mjs",
     "build": "bun -e \"process.exit(0)\"",
+    "ensure:electron": "node ./scripts/ensure-electron.mjs",
     "prepare:opencode-cli": "node ./scripts/prepare-opencode-cli.mjs",
     "verify:opencode-cli": "node ./scripts/verify-opencode-cli.mjs --staged",
     "verify:opencode-cli:packaged": "node ./scripts/verify-opencode-cli.mjs --packaged",
@@ -38,7 +39,7 @@
     "bundle:main": "bun ./scripts/bundle-main.mjs",
     "generate:macos-icon": "node ./scripts/generate-macos-icon-assets.cjs",
     "rebuild:native": "node ./scripts/rebuild-native.mjs",
-    "test:architecture": "node --test ./startup-url-selection.test.mjs ./scripts/target-architecture.test.mjs ./scripts/verify-linux-appimage.test.mjs ./scripts/verify-update-manifest.test.mjs",
+    "test:architecture": "node --test ./startup-url-selection.test.mjs ./scripts/target-architecture.test.mjs ./scripts/verify-linux-appimage.test.mjs ./scripts/verify-update-manifest.test.mjs ./scripts/ensure-electron.test.mjs",
     "test:updater": "node --test ./updater-capability.test.mjs ./updater-channel.test.mjs ./updater-check.test.mjs ./updater-feed.test.mjs ./scripts/finalize-latest-yml.test.mjs ./scripts/updater-e2e-fixture.test.mjs",
     "test:linux-desktop": "node --test ./linux-autostart.test.mjs && node ./scripts/smoke-linux-app-discovery.mjs && node ./scripts/smoke-path-open-utils.mjs",
     "updater:e2e:fixture": "node ./scripts/updater-e2e-fixture.mjs",