Feature request: Configurable file type detection for open file context

Description

When using Claude Code (CLI in VS Code integrated terminal or the extension), the system automatically detects the currently open file and provides context via system-reminder. However, certain file types like .md and .pdf are excluded from this detection.

Current behavior

• Code files (.py, .js, .ts, .txt, etc.) → Detected automatically
• .md and .pdf files → Not detected

Request

Add a configuration option to customize which file types are included in automatic detection. For example:

{
  "claude.openFileDetection.includeExtensions": [".md", ".pdf"],
  "claude.openFileDetection.excludeExtensions": [".log", ".lock"]
}

This would allow users who work heavily with markdown or documentation files to opt-in, while preserving the current default behavior for users who prefer it.

Rationale

• The current behavior likely makes sense for code-focused workflows
• Users with documentation-heavy workflows would benefit from customization
• Manual @file.md references work but add friction when the file is already open

Environment

• Claude Code CLI v2.1.3
• VS Code integrated terminal
• Windows 11