When a critical operation fails (chmod/chown/rmdir/view), the status
line pulses its background between status_bg and theme.error for 400ms.
This gives the user immediate visual confirmation that something went
wrong, even if the message text is short or they aren't looking at
the status bar.
- StatusLine::set_error() — sets message + triggers flash
- StatusLine::error_flash_progress() — remaining fraction (0.0..=1.0)
- blend_bg() — RGB linear interpolation between two Color values
- rgb() — named-color → RGB tuple for interpolation
Wired into 4 critical error paths in dialog_ops.rs (chmod, chown,
rmdir, view). Other transient messages continue to use set_message().
Tests: 1388 pass (was 1384), zero warnings.
vasilito
4325c67471