Support monorepo fragments, export * re-exports, and clearer unresolved-import errors

[jaredly]

Summary:

• Use the resolve package to follow nodejs import resolution
• Extend parser/resolve to support export * from "./..." re-exports when resolving fragments.
• Improve error messaging for unresolved non-relative imports

Code mostly generated with gpt-5.2-codex

Test plan:

• yarn test src/parser/__test__/utils.test.ts
• yarn test src/parser/__test__/parse.test.ts

[changeset-bot]

🦋 Changeset detected

Latest commit: 6cfd6d8

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@khanacademy/graphql-flow	Minor

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[kevinb-khan]

Thanks for create this PR so quickly. I'd like to do some manual testing with this before I review the code. I'll try to do that sometime this week. I'm a little concerned about how we build the module map. During assessment testing periods we have multiple versions of @khan prefixed packages in the repo. I'll have to do some work to track down if there are any duplicate fragments in any of these packages.

[jaredly]

hmmmm so do you think we should be doing full package.json parsing to determine the resolution for an import? I wonder if there's a package for that.

[jaredly]

turns out there was! @kevinb-khan I now think that this solution will support the "assessments uses a pinned version while something else doesn't". however, I don't think we'll currently support 'depending on a fragment that is in a package not in the current repo, but is installed via pnpm' edit: actually maybe this would already work 🤔