chore(io): remove shellexpand and use std::env::home_dir

[Xuanwo]

Summary

• remove shellexpand from workspace and lance-io dependencies
• replace tilde expansion in lance-io with std::env::home_dir-based logic
• keep support for ~ and ~/... paths (plus ~\\... on Windows)
• update lockfile to drop shellexpand

Validation

• cargo check -p lance-io
• cargo test -p lance-io test_tilde_expansion -- --nocapture

[Xuanwo]

Superseded by #5987 from origin branch.

[github-actions]

PR Review

P0 - Use of deprecated std::env::home_dir()

The new expand_tilde_path function uses std::env::home_dir() which has been deprecated since Rust 1.29. The deprecation exists because on Windows, this function checks the HOME environment variable first (which is non-standard on Windows) before falling back to proper Windows APIs, leading to potentially incorrect results.

The workspace already has the dirs crate (v6.0.0) in Cargo.toml:

dirs = "6.0.0"

Suggested fix in rust/lance-io/src/object_store.rs:

fn expand_tilde_path(path: &str) -> Option<std::path::PathBuf> {
    let home_dir = dirs::home_dir()?;  // Use dirs crate instead of std::env::home_dir
    if path == "~" {
        return Some(home_dir);
    }
    // ... rest unchanged
}

And add to rust/lance-io/Cargo.toml:

dirs.workspace = true

This avoids the deprecation warning while using the same underlying implementation that shellexpand was using internally.