[codex] improve search and storage behavior

[rorohecker]

Summary

• make first-pass search more complete by combining indexed, Windows Search, and live-drive results without skipping default Windows roots
• guard and hide semantic search until Local AI models/runtime are installed
• fix tag sidebar drill-ins so saved tag counts open the matching saved paths
• improve storage analyzer rollups and bucket layout for useful highest-level folders

Why

The prior search flow could require a second query to see deeper results, and full-drive search skipped folders that users still expect to be searchable. Tag counts were computed globally, but tag clicks filtered only the current folder. Storage rollups could surface default container folders instead of actionable app/project folders.

Validation

• cargo check
• cargo test storage_tests -- --nocapture