PDF / file support

[brandomagnani]

Body:
When attaching PDFs with @Notation (e.g., @document.pdf), the model can't see the PDF content.

Steps to reproduce:

1. Attach a PDF using @document.pdf
2. Ask about the PDF content
3. Model responds as if no PDF was provided

Problem:
PDFs are read successfully but then dropped in converter.ts (lines 426-427).
The converter only handles 'image' and 'audio' types, not 'file' type.

Affected file:
/packages/core/src/core/openaiContentGenerator/converter.ts

Why is this needed?

• The documentation (docs/cli/commands.md:364) explicitly states: "Multimodal Support: If the path points to a supported image (e.g., PNG, JPEG), PDF, audio, or video file, it
  will be correctly encoded and injected as multimodal input"
• This creates user confusion when PDFs silently fail despite being "supported" per the docs
• Many users work with technical documentation, API specs, and papers in PDF format
• The silent failure wastes time as users don't understand why their PDFs aren't being processed
• Adding PDF support (or at least a clear error message) would make Qwen Code more flexible and useful for real-world development tasks

[pomelo-nwu]

@brandomagnani This is a great feature suggestion. We need some time to evaluate the implementation approach. We're considering several options, such as native multimodal model support, leveraging local tooling for parsing, or a solution similar to Claude's Code Skill.

[pomelo-nwu]

Hi @brandomagnani , By leveraging the document-skill from Claude Code and custom commands in Qwen Code, I can easily parse local PDFs into LLM-friendly Markdown files. You can give it a try too!

Here are the detailed steps:

1. Copy the PDF skill from: https://github.com/anthropics/skills/tree/main/document-skills/pdf to your project’s .qwen/skill/ directory.
2. Create a custom command file: pdf.toml with the following content:

description = "Convert local PDF files to markdown"

prompt = """
You need to thoroughly read the `.qwen/skills/pdf/SKILL.md` file to master the techniques for processing PDF files, and ultimately convert the content to markdown format, saving it to a local .markdown file (create the file if it doesn't exist).
"""

3. Run Qwen Code and use the /pdf command, then input the path to your PDF file.

4. Check the results!