Error handling test

[johnfav03]

Fixes #

[Copilot]

Pull Request Overview

This PR adds a new TypeScript compiler error that prevents comparison operations (except equality) between string literals. The change introduces validation to catch potentially problematic string literal comparisons during compilation.

Key changes:

• Adds a new error diagnostic for string literal comparisons
• Implements compiler logic to detect and report string literal comparison operations
• Creates test case to validate the new error behavior

Reviewed Changes

Copilot reviewed 6 out of 7 changed files in this pull request and generated 2 comments.

File	Description
tests/cases/compiler/StringComp.ts	Test case demonstrating string literal comparison that should trigger the new error
tests/baselines/reference/stringComp.*	Baseline files for the new compiler test (types, symbols, and JS output)
src/compiler/diagnosticMessages.json	New error message for string literal comparison restriction
src/compiler/checker.ts	Compiler logic to detect and report string literal comparison errors

Comments suppressed due to low confidence (2)

[typescript-bot]

With 6.0 out as the final release vehicle for this codebase, we're closing all PRs that don't fit the merge criteria for post-6.0 patches. If you think this was a mistake and this PR fits the post-6.0 patch criteria, please post to the 6.0 iteration issue with details (specifically, which PR and which patch criteria it satisfies).

Next steps for PRs:

• For crash bugfixes or language service improvements, PRs are currently accepted at the typescript-go repo
• Changes to type system behavior should wait until after 7.0, at which point mainline TypeScript development will resume in this repository with the Go codebase
• Library file updates (lib.d.ts etc) continue to live in this repo or the DOM Generator repo as appropriate