docs(files): clarify files.content returns Response object

[dhofheinz]

Changes being requested

Updated documentation for openai.files.content() to clarify that it returns a Response object, not raw file content. The previous JSDoc comment was ambiguous, leading users to expect file content directly.

What changed:

• Enhanced JSDoc comment to explicitly state Response object is returned
• Added documentation for .text(), .blob(), and .arrayBuffer() consumption methods
• Provided two practical code examples in JSDoc
• Created a comprehensive example file demonstrating all consumption patterns

Files modified:

• src/resources/files.ts - Updated JSDoc (lines 66-85)
• examples/file-content-retrieval.ts - New example file (NEW)

Additional context & links

This addresses the 15-month-old issue #958 where users were confused about the return type. The fix follows the exact pattern established in src/resources/audio/speech.ts for documenting Response-returning methods.

Validation:

• ✅ All but one tests passing (680/681)
• ✅ Build successful
• ✅ Linting clean

Fixes #958

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Note: I understand that this repository is auto-generated and my pull request may not be merged. However, this documentation enhancement provides immediate value to users and follows the established patterns in the codebase. The examples/ directory is protected from generator overwrites, ensuring the example file persists.