Feature request: Filter @ mention file suggestions via settings or .claudeignore

Feature Request

When typing @ in the Claude Code prompt box to mention a file, all project files appear in the suggestion list — including folders like dist/, and sensitive paths like .env files.

The current permissions.deny rules in settings.json (e.g. Read(**/dist/**)) do not filter these suggestions — they only block Claude's built-in tools from accessing those paths.

Proposed Solution

Add a way to exclude files/folders from the @ mention autocomplete, either via:

• A .claudeignore file (similar to .gitignore)
• A new settings.json key (e.g. fileSearch.exclude)
• Respecting existing permissions.deny Read rules for the suggestion list

Use Case

Prevents clutter and avoids accidentally referencing sensitive or irrelevant files when using @ mentions.