Remove the hardcoded statusline_offset from calculate_position() and
let padding.y serve as the sole offset from the bottom edge. Bump
default padding.y to 3 to preserve the original visual position.
Add indicator.padding (x, y) to offset the status indicator from the
editor edges. Defaults to 1 cell on each axis, moving the indicator
away from the right edge and bottom of the buffer.
Implement runner module for spawning and managing watchexec child processes
via vim.fn.jobstart with stdout/stderr piping and ANSI stripping. Add
indicator module for displaying a small non-focusable float that shows the
last command outcome (success/failure) when the main window is hidden.