fix(picker.actions): clamp cursor line when the buffer shrank

[truls27a]

Description

M.jump restores the cursor from item.pos, which the finder snapshotted when the picker opened:

vim.api.nvim_win_set_cursor(win, { pos[1], pos[2] })

If the buffer has fewer lines by the time the pick is confirmed, this raises Invalid cursor line: out of range.

Terminal buffers hit it regularly. A terminal buffer has one line per row of the window showing it, and previewing a loaded buffer puts the real buffer in the preview window (picker/preview.lua:110), which resizes the pty down to the preview's height. The position was captured before that, so on confirm M.jump asks for a line the shrunken buffer no longer has.

This clamps the line to the buffer's last line. The column already gets clamped by nvim_win_set_cursor.

Tested with the repro from #2939, and by driving the buffers picker over a buffer that shrinks while the picker is open: before, actions.lua:149: Invalid cursor line: out of range; after, the jump lands on the last line. ./scripts/test passes.

One thing I did not do, since it is a behaviour choice: for buftype == "terminal" it may be better to skip the cursor restore altogether, because the clamped line stops meaning anything as soon as the pty resizes back. Happy to change it to that.

Related Issue(s)

• Fixes bug(picker): jumping to a terminal buffer fails with "Invalid cursor line: out of range" #2939