[Bug] @agent autocomplete includes non-agent files

Bug Description
@agent should only show agents, not unrelated files

Environment Info

• Platform: darwin
• Terminal: ghostty
• Version: 2.0.67
• Feedback ID: aab3d04c-bfaf-45eb-9042-7e57778aa4b9

Errors

[{"error":"Error: NON-FATAL: Lock acquisition failed for /Users/walid/.local/share/claude/versions/2.0.67 (expected in multi-process scenarios)\n    at b8R (/$bunfs/root/claude:2242:2155)\n    at xBA (/$bunfs/root/claude:2242:1875)\n    at processTicksAndRejections (native:7:39)","timestamp":"2025-12-12T21:24:57.562Z"},{"error":"Error: 429 {\"type\":\"error\",\"error\":{\"type\":\"rate_limit_error\",\"message\":\"This request would exceed your account's rate limit. Please try again later.\"},\"request_id\":\"req_011CW3ZhbFGhKJV5jz9hyRwP\"}\n    at generate (/$bunfs/root/claude:411:10636)\n    at makeRequest (/$bunfs/root/claude:749:5434)\n    at processTicksAndRejections (native:7:39)","timestamp":"2025-12-12T22:15:17.154Z"}]

<img width="2242" height="560" alt="Image" src="https://github.com/user-attachments/assets/b3bb3326-e4cd-4f56-b9f4-c84456754d8c" />