fix: use visual column for navigation comparison

The navigation functions compare columns using lines.get_start_col() which
returns visual column (with tab expansion). The current() function in
targets.lua was returning byte column from nodes.get_scol(), causing
sibling detection to fail when files use tabs for indentation.

This fix changes current() to use visual column for the comparison,
using the node's starting row (not cursor row) to handle cases where
cursor is inside a multi-line node that starts on a different line.

Fixes sibling navigation (Up/Down) in files with tab indentation.

Author: ahdzib-maya

lua/treewalker/targets.lua

@@ -1,10 +1,20 @@
 local nodes = require "treewalker.nodes"
 local strategies = require "treewalker.strategies"
 local util = require "treewalker.util"
+local lines = require "treewalker.lines"
 local markdown_targets = require "treewalker.markdown.targets"
 
 local M = {}
 
+-- Get visual column for node's starting position
+-- This matches lines.get_start_col() used in strategies.lua
+-- Needed because get_scol() returns byte column, but strategies uses visual column
+local function get_visual_col(node)
+  local node_srow = nodes.get_srow(node)
+  local line = lines.get_line(node_srow)
+  return line and lines.get_start_col(line) or nodes.get_scol(node)
+end
+
 ---@param node TSNode
 ---@return TSNode | nil, integer | nil
 function M.out(node)
@@ -45,7 +55,7 @@ function M.up(current_node, current_row)
   if util.is_markdown_file() then
     return markdown_targets.up()
   end
-  local current_col = nodes.get_scol(current_node)
+  local current_col = get_visual_col(current_node)
   local candidate, candidate_row = strategies.get_neighbor_at_same_col("up", current_row, current_col, nil, nil)
   return candidate, candidate_row
 end
@@ -57,7 +67,7 @@ function M.down(current_node, current_row)
   if util.is_markdown_file() then
     return markdown_targets.down()
   end
-  local current_col = nodes.get_scol(current_node)
+  local current_col = get_visual_col(current_node)
   local candidate, candidate_row = strategies.get_neighbor_at_same_col("down", current_row, current_col, nil, nil)
   return candidate, candidate_row
 end