Read tool: suggest alternatives when rejecting binary files

Problem

When the Read tool encounters a binary file (e.g., .xlsx, .docx), it returns:

This tool cannot read binary files. The file appears to be a binary .xlsx file.

The message is accurate but unhelpful — the user needs to know what to do instead.

Suggested Fix

Append guidance based on file type:

• .xlsx → "Use a Python script with openpyxl or pandas to read Excel files"
• .docx → "Use a Python script with python-docx to read Word files"
• .pptx → "Use the pptx skill or python-pptx to read PowerPoint files"
• .pdf → "The Read tool supports PDF files — try reading it directly" (if applicable)
• Other binary → "Use a Python script or appropriate CLI tool to process this file"

Impact

Minor UX improvement. Users hit this when they forget the tool's limitations and have to figure out the alternative path themselves. One extra sentence in the error saves a round-trip.

Environment

• Claude Code CLI on Windows 11