chore(FR-2851): drop deprecated/dead babel deps and dead babel.config.js

[yomybaby]

Resolves #7320(FR-2851)

Summary

Three direct dependencies print deprecated warnings on every pnpm install. This PR retires them, and while we're in the file, deletes the dead babel.config.js they were tied to plus the four root babel plugins it was the sole consumer of.

Direct dep changes

• react/package.json: @babel/plugin-proposal-private-property-in-object → @babel/plugin-transform-private-property-in-object (Babel 7.13+ rename, drop-in re-export).
• Root package.json: removed
  • babel-eslint — dead. ESLint 9 flat configs (eslint.config.mjs, react/eslint.config.js, e2e/eslint.config.mjs, packages/backend.ai-ui/eslint.config.js) all use @typescript-eslint/parser + @eslint/js; grep -rn babel-eslint returns zero hits.
  • @babel/plugin-proposal-class-properties — only ever referenced from babel.config.js, which is dead (see below).
  • @babel/plugin-proposal-decorators — same.
  • @babel/plugin-syntax-dynamic-import — same.
  • @babel/parser, @babel/types — no consumer in src/, scripts/, electron-app/, packages/.
• Root babel.config.js: deleted. After the CRA→Vite migration, no build path reads it: @vitejs/plugin-react defaults to configFile: false/babelrc: false and both react/vite.config.ts and packages/backend.ai-ui/vite.config.ts configure babel.plugins inline (babel-plugin-react-compiler + babel-plugin-relay). tsup (used by backend.ai-client) uses esbuild, not babel. There is no babel-loader, @babel/register, or babel-node consumer in the repo.

Why now

Every contributor sees these three warnings on pnpm install and has no way to silence them without editing a direct dependency. The babel.config.js next to them was orphaned and pinning four real packages for nothing.

Lockfile diff

The lockfile shrinks ~10K lines. The shrink is mostly from babel-eslint's 2019-era transitive chain dropping out, but it also drops a few entries that were already orphaned in main's lockfile from the CRA→Vite migration (react-scripts patch chain, @craco/craco, etc.). These had no live consumer; pnpm install simply re-resolves them out. No behavior change.

The legacy plugin-proposal-class-properties@7.18.6 and plugin-proposal-private-property-in-object@7.21.11 entries that remain in the lockfile are pulled in transitively by babel-preset-react-app@10.1.0 (still a react/ devDep). Removing that preset is out of scope for this PR but a reasonable follow-up — it would also let the renamed transform-* direct dep in react/package.json go away.

Verification

• pnpm install no longer prints deprecated warnings for babel-eslint, @babel/plugin-proposal-class-properties, or @babel/plugin-proposal-private-property-in-object.
• bash scripts/verify.sh — Relay / Lint / Format pass. The TypeScript failures shown (packages/backend.ai-client/src/client.ts implicit-any, DeleteForeverVFolderModalV2.tsx BulkPurgeVFoldersV2Input.options) are pre-existing on main (verified by re-running with my changes stashed), unrelated to babel deps.

Test plan

• pnpm install shows no deprecation warnings for the three packages above.
• pnpm run dev starts the dev server without runtime errors related to babel transforms.
• CI passes the same set of checks that pass on main.

[yomybaby]

• feat(FR-2840): migrate to pnpm v11 #7307
• chore(FR-2851): drop deprecated/dead babel deps and dead babel.config.js #7321 👈 (View in Graphite)
• main

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[github-actions]

Coverage Report for react-coverage (./react)

Status	Category	Percentage	Covered / Total
🔵	Lines	6.5%	1783 / 27402
🔵	Statements	5.37%	1978 / 36784
🔵	Functions	5.19%	296 / 5699
🔵	Branches	3.77%	1293 / 34255

File Coverage

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Generated in workflow #487 for commit 3c023bb by the Vitest Coverage Report Action

[Copilot]

Pull request overview

This PR reduces workspace maintenance noise by removing deprecated/unused Babel dependencies and deleting an orphaned root Babel config that is no longer part of the build toolchain after the CRA→Vite migration.

Changes:

• Replaces deprecated @babel/plugin-proposal-private-property-in-object with @babel/plugin-transform-private-property-in-object in react/.
• Removes unused root devDependencies (babel-eslint, several Babel proposal/syntax plugins, and @babel/parser/@babel/types).
• Deletes the unused root babel.config.js.

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated no comments.

File	Description
react/package.json	Swaps the deprecated private-property plugin to the non-deprecated transform variant.
package.json	Drops unused/deprecated Babel-related devDependencies (including babel-eslint).
babel.config.js	Removes an unused Babel configuration file that no longer has an active consumer.

[graphite-app]

Merge activity

• May 8, 2:41 PM UTC: yomybaby added this pull request to the Graphite merge queue.
• May 8, 2:43 PM UTC: Merged by the Graphite merge queue.