feat(md-to-docx): accept pasted Markdown text as input

[Anijesh]

🔀 Pull Request

📌 Issue Reference

Closes #566

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📝 Summary

• What issue does this fix?
  The Markdown → DOCX tool only accepted a .md file upload. Since the Markdown is usually already on the clipboard (or being tweaked right before conversion), users had to save it to a file first just to convert it. This adds a plain text input as an alternative source.

• What major changes were made?

  Backend

  • /convertMdToDocx (backend/blueprints/markdown_docx.py) now resolves its input through the shared resolve_markdown_input() validator, so it accepts either the uploaded file or a new text form field. Pasted Markdown downloads as document.docx; the existing upload flow, the .md extension check and the UTF-8 decode error are unchanged, and blank / whitespace-only text is rejected with 400.
  • Conversion stays fully in memory and uses only local libraries — no disk writes, no external API.

  Frontend

  • MdToDocx.tsx now shows an "Upload .md file" / "Paste Markdown" switch. In text mode the drop area is replaced by a Markdown textarea, and the Convert button stays disabled until something is typed. Switching modes clears the input from the mode you left, so only one source is ever active.

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📸 Screenshots (if applicable)

Verified against the running endpoint rather than screenshots:

text input     -> 200 attachment; filename=document.docx
file upload    -> 200 attachment; filename=readme.docx   (unchanged)
blank text     -> 400 No Markdown provided. Please upload a .md file or enter Markdown text.
empty request  -> 400 No Markdown provided. Please upload a .md file or enter Markdown text.

The generated .docx is a real Word document — unzipping it shows the converted headings and body text in word/document.xml.

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✅ Checklist

• My code follows the project's coding conventions
• I have tested all impacted features
• I have updated or added necessary documentation

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🔗 Related Issues / PRs

Issue #566

Depends on #617 (issue #565), which introduces the shared resolve_markdown_input() validator and the optional ToolPageTemplate props this PR builds on. This branch is stacked on top of it, so the diff here shows both commits until #617 is merged — after that it reduces to the DOCX-only changes automatically. Please merge #617 first.

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🏅 Open Source Program Participation

Program Name: GSSoC '26

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💬 Additional Notes

• Tests: added 3 backend tests to backend/test_blueprints.py (text input success, blank text rejected, empty request rejected) and a new frontend/src/tests/mdToDocxTextInput.test.tsx with 4 tests covering the mode switch. pytest is at 86 passing with no new failures (the 2 pre-existing add_watermark failures are untouched) and vitest at 17 passing. npm run lint, npm run typecheck and npm run build are all clean.
• The Readme.md feature list previously had no entry for Markdown → DOCX at all; this PR adds one.

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