[VS Code Extension] Support IDE selection context for Markdown (.md) files

Feature Request

Description

The VS Code extension currently passes selected text context (ide_selection) only from source code files. Selections made in Markdown (.md) files are not recognized or passed to the conversation context.

Current Behavior

• Selecting text in .cs, .ts, .js, etc. → selection is passed to Claude as ide_selection context
• Selecting text in .md files → selection is not passed; Claude does not see the highlighted content

Expected Behavior

Selections in .md files should also be passed as ide_selection context, the same way source code selections are.

Use Case

Many projects rely heavily on Markdown files for architecture docs, design specs, and project instructions (e.g., CLAUDE.md). Being able to select a specific section and ask Claude about it — just like with code — would be very useful.

Workaround

• Manually copy-paste the relevant section into the chat
• Use @filename.md to attach the entire file (but this includes unnecessary content)