fix: render uploaded file prompts without inline data

[Kayvan Zahiri (Kayvan-Zahiri)]

Prompt.build() raises KeyError: 'file_data' for a chat prompt containing an uploaded PDF reference such as {"type": "file", "file": {"file_id": "{{report_file_id}}"}}. Uploaded files do not require inline file_data (file-input guide).

Render file_data only when present, matching the existing treatment of file_id and filename. Add public Prompt.build() regressions for uploaded and inline files in strict and non-strict mode, checking the complete message payload and preservation of the source template.

Validation:

• Before the fix: the two uploaded-file cases fail with KeyError: 'file_data'; the two inline-file controls pass.
• Logger suite: 199 passed, 4 skipped, 23 subtests passed (Python 3.13.4).
• Final focused prompt/message tests: 13 passed.
• All repository pre-commit hooks passed, including pinned Ruff format/check.

This exercises local SDK prompt rendering; it does not upload a file or make a model request. Tools and dependencies were installed only in an isolated virtual environment. mise is unavailable locally, so the pinned pre-commit hooks were run directly.

AI assistance: Codex identified, reproduced, implemented, and tested this local SDK fix. Submitted as a draft for human review.