This pull request enhances the Linear import tool by adding support for migrating attachments from Trello to native Linear attachments during Trello JSON imports. It introduces new prompts for users to opt into attachment migration and provide Trello API credentials, updates the import pipeline to upload and link attachments, and improves build configuration for better dependency handling.

Trello Attachment Migration Support

• Added an option in the Trello import flow to migrate attachments, prompting for Trello API Key and Token if selected (packages/import/src/importers/trelloJson/index.ts, TrelloJsonImporter class, types) [1] [2] [3] [4] [5] [6].
• Updated the Trello importer to, when enabled, fetch, upload, and link attachments as native Linear attachments instead of just including Trello links in the issue description (TrelloJsonImporter, importIssues.ts) [1] [2] [3] [4] [5] [6].

Import Pipeline Enhancements

• Modified the import pipeline to accept and process attachments, uploading them to Linear and updating issue descriptions to reference the new asset URLs (importIssues.ts, types) [1] [2].

Build and Dependency Updates

• Improved the Rollup build configuration to handle external dependencies and Node.js core modules more robustly, and added ts-node as a dev dependency (rollup.config.js, package.json) [1] [2] [3] [4] [5] [6].

Changelog

• Added a changeset describing the new attachment migration feature for Trello imports (.changeset/poor-plums-dress.md).