fix: decode pmset accessory names as MacRoman

[yuchenzhu-research]

Summary

Fix Bluetooth accessory names containing MacRoman characters being rendered as the Unicode replacement character (�).

For example:

• Expected: yuchen’s Magic Keyboard
• Actual: yuchen�s Magic Keyboard

Root cause

On macOS, pmset -g accps can emit accessory names using MacRoman. Byte 0xD5 represents U+2019 RIGHT SINGLE QUOTATION MARK in MacRoman. macpow decoded the complete stdout buffer with String::from_utf8_lossy, which replaced that byte with U+FFFD.

Changes

• Preserve valid UTF-8 output unchanged.
• Fall back to MacRoman decoding when pmset output is not valid UTF-8.
• Extract Bluetooth output parsing into a testable function.
• Add regression tests for MacRoman and UTF-8 device names.
• Apply a behavior-preserving Rust 1.97 Clippy compatibility refactor.

Verification

• cargo check --release
• cargo fmt --check
• cargo test --lib
• Repository CI Clippy command
• Regression tests for both MacRoman and UTF-8 names
• Manual TUI verification: device names render without replacement characters

Closes #19