[Bug] File mention autocomplete ranking ignores exact filename matches

Bug Description
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Title: @ file-mention autocomplete often ranks the wrong file first, even on exact filename match

Description:
In a large monorepo, typing an exact or near-exact filename after @ (e.g. @types.ts or a full relative path like
@libs/helpers/src/types.ts) frequently doesn't surface the intended file as the top (or any) suggestion. Instead the dropdown
shows unrelated top-level files/directories, forcing manual path-by-path navigation instead of actual search.

Expected: Typing a filename or relative path should fuzzy-match and rank exact/closer matches first, similar to a fuzzy file
finder (fzf-style), regardless of directory depth.

Actual: The dropdown appears to browse the file tree rather than search it — an exact filename typed in full sometimes still
doesn't appear as the top suggestion, and deep nested paths require typing each directory segment correctly to narrow down.

Environment: Large Nx monorepo (many nested apps/, libs/ projects, node_modules).

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Environment Info

• Platform: darwin
• Terminal: kitty
• Version: 2.1.233
• Feedback ID: 5aa87919-29c7-46df-a18a-7a405cb57ebd

Errors

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