agy animates an 8-dot braille spinner (⣯ ⡿ ⣻ ⣾ ⣷ ⣟ ⢿ ⣽) with a label one row above
the composer, none of which is in SPINNER_PATTERN, and the entry declared no
workDetect, so no frame ever marked a tab working.
Declare the working line from the live pane and the footer hint `? for shortcuts`
as the idle-arming mark. The composer's `>` cannot be the glyph: the echoed
prompt starts with it too. Tests use verbatim captures from agy 1.3.3.