fix(treesitter): get_node_text() inconsistent trailing newline #39409

Problem:
`get_node_text()` returned inconsistent results between buffer and
string sources when a node's range ends at `end_col == 0` (i.e. the node
ends with a newline). The buffer path dropped the trailing newline; the
string path included it correctly.

Solution:
Append `'\n'` in `buf_range_get_text()` when `end_col == 0` and
`start_row ~= end_row`. The `start_row ~= end_row` guard excludes
zero-width nodes at column 0, which should return `""`.

Remove the workaround in the `#trim!` directive that manually
compensated for the missing newline.

Strip whitespace in `resolve_lang()` so injection language nodes ending
at `end_col == 0` (e.g. `">lua\n"`) still resolve correctly.

runtime/lua/vim/treesitter/query.lua

@@ -706,10 +706,6 @@ local directive_handlers = {
     local start_row, start_col, end_row, end_col = node:range()
 
     local node_text = vim.split(vim.treesitter.get_node_text(node, bufnr), '\n')
-    if end_col == 0 then
-      -- get_node_text() will ignore the last line if the node ends at column 0
-      node_text[#node_text + 1] = ''
-    end
 
     local end_idx = #node_text
     local start_idx = 1