view tool rejects a normal 8.6 KB file as too large to read at once

Describe the bug

The built-in view tool (shown as Read in the VS Code UI) reports File too large to read at once (8.6 KB) when asked to read a small, ordinary multiline Markdown file. This appears to be a false-positive size warning and makes normal full-file inspection unnecessarily cumbersome.

This is not the large single-line JSON or custom-tool-output case. The file is a regular Markdown document and is approximately 8.6 KB.

Affected version

Unknown - encountered in the Copilot CLI runtime integrated with VS Code.

Steps to reproduce the behavior

1. Use the Copilot CLI runtime in VS Code on Windows.
2. Ask the agent to read a normal multiline Markdown file of approximately 8.6 KB.
3. Allow the built-in view/Read tool to read the file without specifying a range.
4. Observe the File too large to read at once (8.6 KB) warning instead of the file contents.

Expected behavior

A normal file of this size should be read successfully in full. If a size threshold is required, the threshold should be consistent, documented, and should not report ordinary small files as too large without a clear reason.

Additional context

• OS: Windows 11
• Host: Visual Studio Code
• Tool: built-in view/Read
• File type: regular Markdown, approximately 8.6 KB
• The warning recommends using view_range, even though the file is small enough that a full read would normally be expected.
• This report is about the view tool's full-file size handling, not Azure DevOps or the repository being inspected.

定位内置的 view/Read 实现和完整文件大小检查，然后在所述的 Windows 和 VS Code 设置中，使用一个约 8.6 KB 的多行 Markdown 文件重现该问题。追踪为什么这个正常文件会被拒绝；完成的标准是文件能够完整读取且不会出现误报警告，同时真正过大的输入或单行输入仍得到适当处理。