fix: correct validation diagnostic highlight range

[cyphercodes]

Summary

• Fix validation diagnostic range end positions to use zero-based LSP offsets
• Add regression coverage so invalid field highlights stop before trailing whitespace
• Add a patch changeset for graphql-language-service

Fixes #4234.

Tests

• yarn vitest run packages/graphql-language-service/src/interface/tests/getDiagnostics.test.ts
• yarn tsgo --build packages/graphql-language-service/tsconfig.json
• yarn vitest run packages/graphql-language-service/src
• yarn turbo run test --filter=graphql-language-service
• yarn turbo run types:check --filter=graphql-language-service
• yarn oxfmt --check packages/graphql-language-service/src/interface/getDiagnostics.ts packages/graphql-language-service/src/interface/tests/getDiagnostics.test.ts .changeset/loud-fields-dance.md
• git diff --check

[changeset-bot]

🦋 Changeset detected

Latest commit: 2717712

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
graphql-language-service	Patch
codemirror-graphql	Patch

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[linux-foundation-easycla]

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