fix(openapi): infer binary responses from media types

[ngyna]

Closes #17415.

OpenAPI 3.1 raw ZIP/PDF responses and unencoded binary component schemas now retain Fern's existing file/string-binary representation without requiring legacy type: string / format: binary hints.

• Infer operation response transport from parsed media types in both normal workspace conversion and the current importer.
• Lower otherwise shape-free, unencoded binary component schemas to the established binary string primitive without overriding typed, encoded, text/XML, or structural schemas.
• Cover both importer paths with inline/referenced responses and positive/negative component cases.

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[nitpickybot]

AI Review Summary

Adds media-type-driven binary inference in both the legacy and v3 importers, plus a heuristic for typeless contentMediaType schemas. Logic is duplicated verbatim across two packages, the new early-return in ResponseBodyConverter bypasses the existing media-type parsing path (including any streaming handling), and the !isXML() carve-out makes the two importers disagree on image/svg+xml (visible in the two new snapshots: baseline → fileDownload, v3 → empty object).

• 🔴 1 critical issue(s)
• 🟡 2 warning(s)
• 🔵 2 suggestion(s)

[devin-ai-integration]

Devin Review found 1 potential issue.

View 2 additional findings in Devin Review.