chore(deps): replace rollup with rolldown

[devin-ai-integration]

Description

Refs: Requested by @Swimburger
Link to Devin run

Replaces tsup (which uses esbuild + rollup) with tsdown@0.20.3 (which uses rolldown@1.0.0-rc.3) across the monorepo. Replaces esbuild-plugin-polyfill-node with @rolldown/plugin-node-polyfills@1.0.3.

Changes Made

Bundler migration

• Replace tsup@^8.5.0 with tsdown@0.20.3 in 6 package.json files (root, generator-cli, configs, cli, cli-v2, seed)
• Update @rolldown/binding-darwin-arm64 from 1.0.0-rc.2 to 1.0.0-rc.3, add @rolldown/binding-linux-x64-gnu@1.0.0-rc.3
• Update all build scripts to use import { build } from "tsdown" instead of import tsup from "tsup" / tsup.build()
• Rename tsupOverrides → tsdownOverrides, tsupOptions → tsdownOptions, PRODUCTION_TSUP_OVERRIDES → PRODUCTION_TSDOWN_OVERRIDES across all build callers
• Replace esbuildOptions (conditions) with inputOptions.resolve.conditionNames in seed/build.mjs
• Replace esbuild-plugin-polyfill-node with @rolldown/plugin-node-polyfills in configs/build-utils.mjs (buildDynamicSnippets)
• Add keytar to FULL_EXTERNALS and MINIMAL_EXTERNALS in both cli and cli-v2 (native .node binaries cannot be bundled by rolldown)
• Add inlineOnly: false to all tsdown build configs (required to suppress tsdown 0.20.3 dependency bundling warning)
• Add outputOptions: { codeSplitting: false } to single-entry CJS builds (cli, cli-v2, seed, configs) to prevent circular chunk dependencies at runtime
• Remove metafile: true from production build overrides (not supported by tsdown)
• Updated FULL_EXTERNALS regex from /^tsup/ to /^tsdown/
• Update generator-cli bin/cli to require ../dist/cli.cjs (tsdown outputs .cjs not .js)
• Update generator-cli package.json main/types to dist/api.cjs / dist/api.d.cts

Build fixes

• Add missing tsconfig project references (root tsconfig.json, cli-logger, swift/dynamic-snippets, python-v2/sdk)
• Remove unused ir-sdk reference from typescript/model/union-generator/tsconfig.json
• Add "sideEffects": false to rust/dynamic-snippets/package.json

Test updates

• Update ETE test snapshots (auto-generated example IDs changed due to different bundler hashing)
• Update v2 test expectation: validation message changed from "edition is required" → "edition must be a string"

⚠️ Key Areas for Review

1. Bundle size: The CLI bundle is ~36.9MB. Reviewer should verify this is acceptable compared to the previous tsup build.
2. Validation message change: The CLI v2 fern check now reports "edition must be a string" instead of "edition is required" for an invalid fern.yml. This is a behavioral change caused by rolldown bundling the validation library differently. Reviewer should verify this is acceptable.
3. keytar externalization: Added to both cli and cli-v2 externals to prevent bundling native .node files. Verify runtime behavior.
4. codeSplitting: false: Only applied to single-entry builds. generator-cli has multiple entries and cannot use this option — verify no circular dependency issues at runtime.
5. @rolldown/plugin-node-polyfills (packages/configs/build-utils.mjs): Replaces esbuild-plugin-polyfill-node for browser builds. Verify dynamic snippets work correctly.
6. inputOptions.resolve.conditionNames (packages/seed/build.mjs): Verify rolldown respects this the same way esbuild respects conditions.
7. Non-required seed test failures: go-sdk, ts-sdk, csharp-sdk seed tests are failing (non-required). May warrant investigation.

Testing

• pnpm install completes successfully
• pnpm run check (biome lint) passes
• Local pnpm run fern:build completes successfully
• Local CLI runs: node packages/cli/cli/dist/prod/cli.cjs --version works
• ETE tests pass locally with updated snapshots
• All 7 required CI checks pass (compile, test, lint, biome, depcheck, validate versions, test-ete)

[devin-ai-integration]

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[github-actions]

🌱 Seed Test Selector

Select languages to run seed tests for:

• Python
• TypeScript
• Java
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• Swift
• Rust
• OpenAPI
• Postman

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[Swimburger]

This is not guaruanteed to be for a production env

[devin-ai-integration]

Good catch - removed the hardcoded process.env.NODE_ENV define. The nodePolyfills() plugin handles process polyfilling now.