`@` autocomplete never fetches files on first open — files appear only after the query text changes

Description

Pressing @ once shows only agents/references — no files. Files appear only after typing a character (or pressing @ a second time). Same user-facing symptom as #6618.

Root cause in packages/tui/src/component/prompt/autocomplete.tsx: the files resource refetches only when search() changes. At mount the fetcher runs once while store.visible === false and hits the if (!store.visible ...) return [] guard. Opening the popup with an empty query doesn't change search ("" → ""), so no refetch ever happens on open — the stale empty result is shown. Pressing @ again changes the query to "@" (which fff treats as an empty query), triggering the first real fetch, so files suddenly appear.

OpenCode version

1.18.15

Steps to reproduce

1. Open the TUI in any project directory.
2. Press @ once → popup shows agents/references only, no files.
3. Press @ again (or type any character) → files appear.

Expected behavior

Opening the @ popup fetches the current file list. Fix options: include store.visible in the resource source so opening triggers a fetch, or call files.refetch() in show().

Operating System

Linux (WSL2)

Terminal

Windows Terminal / bash