API: add checker methods to get true and false types of a conditional type

[piotrtomiak]

No description provided.

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Adds API surface to retrieve the true/false branch types of a conditional type through the Checker, wiring it through the Go RPC layer and exposing it in both sync and async TypeScript clients.

Changes:

• Exported Checker.GetTrueTypeOfConditionalType / Checker.GetFalseTypeOfConditionalType in Go.
• Added new RPC methods/handlers and proto method registration for both operations.
• Added sync/async TypeScript client methods plus corresponding tests.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
internal/checker/exports.go	Exposes conditional-type branch getters on the public Checker API.
internal/api/session.go	Routes and implements new RPC handlers that resolve a type handle and return the corresponding branch type.
internal/api/proto.go	Registers two new RPC method names and their unmarshallers.
_packages/native-preview/src/api/sync/api.ts	Adds sync TS client methods for conditional-type true/false branches.
_packages/native-preview/src/api/async/api.ts	Adds async TS client methods for conditional-type true/false branches.
_packages/native-preview/test/sync/api.test.ts	Adds sync test coverage validating branch types for a conditional type alias.
_packages/native-preview/test/async/api.test.ts	Adds async test coverage validating branch types for a conditional type alias.

[mrazauskas]

Could you link to #2851, please?

I was suggesting adding .getTrueType() and .getFalseType() to ConditionalType, but anyway this would solve the same problem.

[piotrtomiak]

@mrazauskas - what do you mean by link? In the git commit message?

I was suggesting adding .getTrueType() and .getFalseType() to ConditionalType, but anyway this would solve the same problem.

I am planning to make this change once #4341 is merged, since this requires association between Type and projectId on the API side, which is now missing

[mrazauskas]

what do you mean by link?

I was thinking that this PR could close #2851, but I’m not sure about that anymore. Feels like these are different domains. One can only guess, because the motivation of the PR is missing (not saying that it is required or so).