Fix declaration emit crash on export assigned arrow function using external name

[weswigham]

Fixes #4629.

Fixing the panic (which is just the change to add the expression kinds to the message lookup helper, since we transform those now) revealed that we weren't reusing the input type node at all, which is why there was an error at all. The rest of the change is adjusting the transformer to transform to a variable statement instead of a function declaration when the whole assignment has a type node.

[Copilot]

Pull request overview

Fixes a declaration emit crash in the Go port when emitting .d.ts for a CommonJS module.exports = (x) => {} where the parameter type references an external module name (via import("...")), and adds a compiler regression test + baselines to prevent recurrence.

Changes:

• Add a compiler regression test exercising a JS module.exports arrow function annotated with a JSDoc function type referencing import("@jest/types").Config.InitialOptions.
• Extend declaration-emit accessibility diagnostics to handle parameters whose parent is an ArrowFunction or FunctionExpression (preventing the reported panic).
• Adjust export-assignment transformation to reuse a full signature type node by emitting a const variable statement rather than always emitting a function declaration.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
internal/transformers/declarations/transform.go	Passes assignment type info into function-like export assignment transforms and may emit declare const to reuse a full signature type node.
internal/transformers/declarations/diagnostics.go	Prevents panic by handling ArrowFunction/FunctionExpression parents for parameter visibility diagnostics.
testdata/tests/cases/compiler/declarationEmitJsExportAssignedArrowNoCrash.ts	New regression test reproducing the crash scenario.
testdata/baselines/reference/compiler/declarationEmitJsExportAssignedArrowNoCrash.types	Expected type baseline for the new regression test.
testdata/baselines/reference/compiler/declarationEmitJsExportAssignedArrowNoCrash.symbols	Expected symbols baseline for the new regression test.
testdata/baselines/reference/compiler/declarationEmitJsExportAssignedArrowNoCrash.js	Expected emit baseline (including generated .d.ts) for the new regression test.