v0.2.5: Clean up library API for external consumers
- Remove all eprintln from library code (open, drop) — library is now silent
- Move CLI-only error variants (InvalidArgument, MissingArgumentValue) to main.rs
- Remove SETTING_APPLY_DELAY from public exports — CLI implementation detail
- Extract AT command framing into pure testable functions with 7 unit tests
- Propagate errors in read_firmware_version and read_hid_typed instead of swallowing
- Add BCD nibble validation for 4K S firmware version decoding
- Feature-gate ureq behind update-check so lib consumers don't pull in HTTP client
- Add rust-version = 1.85 to Cargo.toml (required by edition 2024)
- Update license to GPL-3.0-or-later
- Skip redundant delay after last setting in CLI