Switch Glob to rg with fallbacks and backend logging

[wgqqqqq]

Summary

• switch Glob local execution to prefer rg --files --glob while keeping a Rust walker fallback when rg is unavailable
• switch remote Glob execution to prefer rg and fall back to find when the remote host does not have ripgrep installed
• add explicit backend-selection logs so session logs show whether Glob ran via rg, remote rg, fallback walker, or remote find

Why

• align Glob behavior more closely with the Claude-style ripgrep-backed implementation
• avoid hard failure on local or remote environments that do not have rg
• make backend choice observable in runtime logs for verification and debugging

Validation

• cargo test -q -p bitfun-core glob_tool