Fix off-by-one truncation in union type display

[Andarist]

fixes #3647

[Andarist]

https://github.dev/microsoft/TypeScript/blob/f350b52331494b68c90ab02e2b6d0828d2a22a74/src/compiler/checker.ts#L7921-L7936

[Copilot]

Pull request overview

Fixes a behavioral mismatch in tsgo’s type display truncation logic (notably affecting TS7053 diagnostics) by correcting an off-by-one in the “... N more ...” elision calculation and adding a regression test to lock in the expected output.

Changes:

• Fix off-by-one logic in NodeBuilderImpl.mapToTypeNodes when emitting truncated type lists (union/intersection/type-arg lists).
• Add a new compiler test case covering union element error truncation.
• Update affected reference baselines (compiler, fourslash quick info, and a submodule baseline) to reflect the corrected display output.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
internal/checker/nodebuilderimpl.go	Fixes the truncation/elision count calculation and the truncation trigger condition for type list rendering.
testdata/tests/cases/compiler/unionElementErrorTruncation.ts	Adds a regression test that reproduces the union truncation count mismatch seen in #3647.
testdata/baselines/reference/compiler/unionElementErrorTruncation.errors.txt	New expected diagnostic output for the new regression test.
testdata/baselines/reference/compiler/unionElementErrorTruncation.js	New expected emit baseline for the new regression test (includes .d.ts section due to @declaration: true).
testdata/baselines/reference/compiler/unionElementErrorTruncation.symbols	New expected symbols baseline for the new regression test.
testdata/baselines/reference/compiler/unionElementErrorTruncation.types	New expected types baseline for the new regression test.
testdata/baselines/reference/fourslash/quickInfo/quickinfoVerbosityNoErrorTruncation1.baseline	Updates quickinfo truncation text to reflect corrected “... N more ...” counts.
testdata/baselines/reference/submodule/compiler/declarationEmitPrivatePromiseLikeInterface.js	Updates a declaration emit baseline affected by the adjusted truncation behavior.
testdata/baselines/reference/submodule/compiler/declarationEmitPrivatePromiseLikeInterface.js.diff	Updates the corresponding .diff baseline for the same truncation-related output change.