fix(cli): flatten direct OpenAPI union references

[uuzzrm]

What does this PR do?

Fixes langfuse/langfuse#14609.

The OpenAPI patch script only flattened discriminated oneOf schemas when each branch used the older allOf wrapper shape. The current prompt schemas use direct component references instead. As a result, langfuse api prompts create --help exposed no request-body flags and the documented type, name, and prompt example failed.

This change:

• extracts the union flattening logic into a small testable module;
• supports direct component-reference branches when their schemas expose a single-value enum discriminator;
• keeps the existing allOf form working;
• leaves untagged oneOf schemas untouched;
• regenerates the bundled OpenAPI spec for the prompt and chat-message schemas.

Validation

• bun test scripts/patch-openapi-logic.test.ts
• bun test — 19 tests, 145 assertions
• bun scripts/patch-openapi.ts (idempotent on the patched spec)
• bun build src/cli.ts --outdir /tmp/langfuse-cli-14609-dist --target node --format esm
• Verified prompts create --help shows --type, --name, and --prompt
• Verified --curl produces the expected JSON body without making a network request
• git diff --check

AI-assisted development was used for investigation and implementation; the fix and test suite were run locally against this checkout.

[claude]

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