fix(ui): make title metrics font-safe on Linux

[debpalash]

What changed

• replace Unicode block gauges, thin divider, and em dash in the native window title with compact ASCII text
• remove proportional-font space padding so labels stay attached to their values
• hide the Linux energy field because /proc has no wakeup/energy counter and the old value only duplicated CPU
• keep the macOS energy impact score where TASK_POWER_INFO provides the required counters
• add exact-output and printable-ASCII regressions for the reported machine values

Linux now renders: Opal - Play everything | CPU 15% | MEM 183 MB | THR 47

Verified

• zig build test (1,704 tests)
• zig build -Doptimize=ReleaseSafe
• focused title-meter and brand feature regressions
• git diff --check