sl0p: per-pane status bar via OSC 5577 (experimental)

First slice of the status/action frame: one row of program-supplied text in a
pane's bottom frame row.

    printf '\033]5577;1;status;building 3/7\033\\'
    printf '\033]5577;1;clear\033\\'

Rendered in the EXISTING frame row rather than in reserved rows. Reserving would
shrink the pane's content area and resize its PTY whenever the bar appeared or
disappeared, firing SIGWINCH at the program that asked for it -- the same churn
that made the stack-list picker use a fixed cap. The frame row is already a text
surface with a precedence chain, so this cost no geometry work at all.

State lives on Grid like the window title, so it survives re-renders, resizes
and detach/reattach with no draining. Session resurrection is NOT covered yet.

Versioned from the start, and unknown versions or verbs are ignored, so the
planned button verbs cannot be half-interpreted by an older build. Text is the
remaining params rejoined with ';', which means a single text field needs no
escaping -- the trick OSC 0/2 already uses for titles.

Treated as untrusted, because it is: an in-band sequence is emitted just as
readily by `cat` of a hostile file as by a cooperating program. Control
characters are stripped -- a raw ESC could otherwise repaint anything on screen,
a newline would corrupt the frame row -- and the length is capped, since the
string is retained for the life of the pane.

0 files changed, 0 insertions, 0 deletions