[api] Add missing checker methods

[andrewbranch]

Closes #3610

The one bit of new implementation code is a port of some JSDoc functions from Strada. They weren't originally ported because internally, they were used for creating SymbolDisplayPart[] for hover; instead, similar methods were created for rendering markdown. I didn't want to reintroduce SymbolDisplayPart, but I thought returning the tags in structured form would still be useful, so where Strada returned an array of the following for Symbol.getJSDocTags():

interface JSDocTagInfo {
  name: string;
  text?: SymbolDisplayPart[];
}

Corsa returns an array of:

interface JSDocTagInfo {
  name: string;
  text?: string;
}

[Copilot]

Pull request overview

This PR extends the native-preview IPC API surface to cover additional TypeChecker-like methods and Symbol documentation helpers needed by transpiler consumers (per #3610), including a new JSDoc tag representation that returns plain strings instead of SymbolDisplayPart[].

Changes:

• Added new API endpoints and client wrappers for checker methods like isArrayType, getBaseConstraintOfType, getPropertyOfType, getConstantValue, getSignatureFromDeclaration, getExportSpecifierLocalTargetSymbol, getAliasedSymbol, and getExportsOfModule.
• Introduced Symbol.getDocumentationComment(checker) and Symbol.getJsDocTags(checker) backed by new language-service helpers that render docs/tags as plain text.
• Added sync + async native-preview tests covering the new methods and behaviors.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
internal/ls/jsdoc.go	New LS helpers to extract documentation comment text and structured JSDoc tags as plain strings.
internal/checker/exports.go	Exposes Checker.IsArrayType wrapper to support the new API endpoint.
internal/api/session.go	Adds request dispatch + handlers for the newly exposed checker/symbol methods (including JSDoc endpoints).
internal/api/proto.go	Adds new method constants and request/response parameter types (incl. JSDocTagInfo).
_packages/native-preview/test/sync/api.test.ts	Adds sync API coverage for the new checker methods and symbol JSDoc/documentation behavior.
_packages/native-preview/test/async/api.test.ts	Adds async API coverage mirroring the sync tests for the same new methods.
_packages/native-preview/src/api/sync/types.ts	Adds JSDocTagInfo type for the sync client surface.
_packages/native-preview/src/api/sync/api.ts	Adds sync client wrappers for new checker endpoints + symbol helpers.
_packages/native-preview/src/api/async/types.ts	Adds JSDocTagInfo type for the async client surface.
_packages/native-preview/src/api/async/api.ts	Adds async client wrappers for new checker endpoints + symbol helpers.

[jakebailey]

Is this equivalent to existing code but we just say plaintext like LSP? can that save code?

[andrewbranch]

No; this still separates tag names from comments.