fix(terminal): clamp tooltip dimensions to available screen space

Prevent tooltip from overflowing when the cursor is near the bottom or
right edge of the screen by clamping width and height to the remaining
space.

lua/jj/ui/terminal.lua

@@ -325,6 +325,7 @@ function M.run_floating(cmd, keymaps)
 			{ modes = { "n", "v" }, lhs = "i", rhs = function() end },
 			{ modes = { "n", "v" }, lhs = "c", rhs = function() end },
 			{ modes = { "n", "v" }, lhs = "a", rhs = function() end },
+			{ modes = { "n", "v" }, lhs = "<S-a>", rhs = function() end },
 			{ modes = { "n", "v" }, lhs = "u", rhs = function() end },
 		}
 
@@ -577,6 +578,20 @@ function M.run_tooltip(cmd, tool_opts)
 		state.tooltip_buf = nil
 	end
 
+	local height = tool_opts.height
+	if height then
+		local cursor_screen_row = vim.fn.screenrow()
+		local available = vim.o.lines - cursor_screen_row - 2
+		height = math.min(height, math.max(available, 1))
+	end
+
+	local width = tool_opts.width
+	if width then
+		local cursor_screen_col = vim.fn.screencol()
+		local available = vim.o.columns - cursor_screen_col - 2
+		width = math.min(width, math.max(available, 1))
+	end
+
 	state.tooltip_buf, state.tooltip_win = buffer.create_float({
 		title = tool_opts.title or " JJ ",
 		title_pos = "center",
@@ -585,8 +600,8 @@ function M.run_tooltip(cmd, tool_opts)
 		relative = "cursor",
 		row = 1,
 		col = 0,
-		width = tool_opts.width,
-		height = tool_opts.height,
+		width = width,
+		height = height,
 		win_options = {
 			wrap = true,
 			number = false,