[shps951023]

Purpose of the pull request

Related: #1290

Hello Fesod team,

I would like to contribute lightweight streaming Excel-to-PDF conversion, starting with XLSX, without requiring Microsoft Office or LibreOffice.

This draft adds a design proposal for community feedback before implementation. It does not implement conversion, introduce a public API, add a Maven module, or change dependencies. The proposed scope, PDF backend, and supported scale remain open for discussion.

Thank you for your feedback!

What's changed?

• Add STREAMING_XLSX_TO_PDF_PROPOSAL.md with the proposed initial formatting and pagination scope and explicit non-goals.
• Describe an optional fesod-pdf module, repeatable file-backed input, metadata pre-scanning, and opt-in reader metadata.
• Distinguish row streaming from PDF-generation memory behavior; propose evaluating the backend through page generation and final save before selecting it.
• Document resource ownership, error reporting, proposed validation criteria, implementation stages, and questions for community feedback.

Validation:

• git diff --cached --check - passed.
• Verified that the branch contains one added Markdown document and no unrelated cache-selector changes.
• Maven tests, builds, and website checks were not run: this is a root-level design-document change with no Java, POM, or website changes. No PDF conversion or performance results are claimed.

Checklist

• I have read the Contributor Guide.
• I have written the necessary doc or comment.
• I have added the necessary unit tests and all cases have passed.