[Bug] @ mention file search excludes git submodules in v2.0.72

Bug Description
Bug Report: @ mention file search broken for git submodules in v2.0.72
Version: Claude Code 2.0.72
Environment:

Workspace: Git repository with submodules
Multiple submodule projects in the workspace

Issue:
After upgrading to v2.0.72, the @ file mention feature no longer searches or suggests files within git submodules. Only files in the root repository are searchable.
Suspected Cause:
This regression likely stems from the v2.0.72 optimization: "Improved @ mention file suggestion speed (~3x faster in git repositories)". The performance improvement may have inadvertently excluded submodule directories from the file search index.
Expected Behavior:
The @ command should search and suggest files from both the main repository and all linked submodules, as it did in previous versions.
Actual Behavior:
Files within submodule directories are not appearing in @ mention suggestions, making it impossible to reference them directly.
Steps to Reproduce:

Open a git repository containing one or more submodules
Type @ followed by a filename that exists in a submodule
Observe that no matching files from submodules appear in suggestions

Impact:
This significantly impacts workflows in monorepo-style projects that rely on submodules for code organization.

Environment Info

• Platform: darwin
• Terminal: vscode
• Version: 2.0.73
• Feedback ID: 92eddafe-2d6b-41cf-bfeb-36f4fd5d1ff1