fix(formatter/grep): normalize grep input handling

Normalize parts in resolve_grep_string to safely convert nil, vim.NIL, numbers, and booleans to strings and prefer input.path over input.include when present. This prevents invalid grep strings from non-string inputs.

Author: sudo-tee

lua/opencode/ui/formatter/tools/grep.lua

@@ -4,11 +4,30 @@ local M = {}
 ---@param input GrepToolInput|nil
 ---@return string
 local function resolve_grep_string(input)
+  local function normalize_part(value)
+    if value == nil or value == vim.NIL then
+      return ''
+    end
+
+    local value_type = type(value)
+    if value_type == 'string' then
+      return value
+    end
+    if value_type == 'number' or value_type == 'boolean' then
+      return tostring(value)
+    end
+
+    return ''
+  end
+
   if not input then
     return ''
   end
-  local path_part = input.path or input.include or ''
-  local pattern_part = input.pattern or ''
+  local path_part = normalize_part(input.path)
+  if path_part == '' then
+    path_part = normalize_part(input.include)
+  end
+  local pattern_part = normalize_part(input.pattern)
   return table.concat(
     vim.tbl_filter(function(p)
       return p ~= nil and p ~= ''