fix(install): default to ~/.local/bin for unprivileged installs

[stevensmith37]

Summary

Change the default INSTALL_DIR from /usr/local/bin to $HOME/.local/bin so the script works without sudo. Also move mkdir -p before the privilege check so a non-existent directory doesn't fail the writability test.

Changes

• Changes the INSTALL_DIR to a location that doesn't require admin permissions to write to.
• Changes the location of the directory creation to before the binary installation.

Test plan

• make build passes
• make test passes
• CI green

Rollback plan

Revert this PR.

[mrmaxsteel]

Review

Bug: mkdir -p before check_privileges defeats the privilege check

The PR moves mkdir -p "$INSTALL_DIR" before check_privileges(). The problem is that check_privileges() tests [ ! -w "$INSTALL_DIR" ] — if mkdir -p just created the directory, it will always be writable by the current user, so the privilege check will never fail, even when the user sets INSTALL_DIR to somewhere they shouldn't be writing (e.g., INSTALL_DIR=/usr/local/bin).

The original code had mkdir -p after the privilege check intentionally — it only creates the directory once we've confirmed we have write access to the parent.

The real fix for "non-existent directory fails the writability test" is to check writability of the parent directory when the target doesn't exist yet, not to create the directory preemptively. Something like:

check_privileges() {
    TARGET="$INSTALL_DIR"
    # If the directory doesn't exist, check the closest existing parent
    while [ ! -d "$TARGET" ]; do
        TARGET=$(dirname "$TARGET")
    done
    if [ ! -w "$TARGET" ]; then
        ...
    fi
}

Minor: ~/.local/bin may not be on $PATH

Many systems (macOS in particular) don't have ~/.local/bin on $PATH by default. The script checks command -v mindspec after install, which would fail and show a confusing success-then-not-found experience. Worth adding a PATH hint after install if $INSTALL_DIR isn't on $PATH.

Summary

The default change to ~/.local/bin is a good idea, but the mkdir -p reorder introduces a bug that silently bypasses the privilege check. Recommend fixing check_privileges to walk up to the nearest existing parent directory instead.