fix(typescript-fetch): skip scalar enum comparison for array-typed properties in instanceOf

[mstojanovic8]

Required properties typed as Array<SingleValueEnum> triggered two bugs in the instanceOf guard (side effect of #23497):

1. The enum-literal check fired for array properties — comparing value['types'] !== 'x' against an array is always truthy, permanently breaking instanceOf.
2. For array properties, isString resolves against the container type (Array), not the item type, so the literal was emitted unquoted (boatbooker_activities instead of 'boatbooker_activities'), causing TS2304: Cannot find name.

Fix: wrap the enum-literal block in {{^isContainer}} so it only fires for scalar properties. Scalar enum behavior is unchanged.

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Apologies for the burst of PRs in a short time — we are integrating this generator into production at FishingBooker and kept uncovering issues along the way.
Also sorry for skipping a prior issue on this one; if a release is coming soon we'd love to see it included. Happy to open a follow-up issue if preferred.

Fixes a regression introduced by #23497.

PR checklist

• Read the contribution guidelines.
• Ran unit tests: ./mvnw test -pl modules/openapi-generator -Dtest=TypeScriptFetchClientCodegenTest
• Regenerated typescript-fetch samples: ./bin/generate-samples.sh ./bin/configs/typescript-fetch*
• @mention the technical committee members.

cc @TiFu @taxpon @sebastianhaas @kenisteward @Vrolijkx @macjohnny @topce @akehir @petejohansonxo @amakhrov @davidgamero @mkusaka @joscha @dennisameling

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Summary by cubic

Fixes the instanceOf guard in typescript-fetch to skip scalar enum comparisons for array-typed enum properties (e.g., Array<SingleValueEnum>), preventing false negatives and TypeScript literal name errors. Scalar enum behavior is unchanged.

• Bug Fixes
  • Wrapped the enum-literal check with {{^isContainer}} in modelGeneric.mustache so array enums no longer emit invalid !== comparisons or unquoted literals.
  • Added a test (testInstanceOfArrayEnumNoScalarComparison) with a minimal OpenAPI fixture to verify no scalar comparison is emitted and the field presence check remains.

^{Written for commit 6018a9d. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 4 files

_{Re-trigger cubic}

[wing328]

tested locally and the change looks good.

thanks for the fix

[wing328]

cc @jasperpatterson who's the author of #23497.

[wing328]

Apologies for the burst of PRs in a short time — we are integrating this generator into production at FishingBooker and kept uncovering issues along the way.

We appreciate you and your team contributing back to make this project better.