feat: add hover support for member access with comments

- Add member access chain resolution in hover handler
- Parse #var.member.submember notation and resolve type chain
- Show member comments in hover tooltip
- Extract comments from UDT and DB file fields
- Combine all type sources (doc.types, external_types, builtin)

src/plc_json.lua

@@ -212,9 +212,11 @@ local function parse_scl_type_file(content)
           local field_name = line:match("^%s*(%w+)%s*:")
           if field_name and field_name ~= "END_STRUCT" then
             local field_type = line:match(":%s*([%w_]+)")
+            local field_comment = line:match("//%s*(.+)$") or line:match("%(%*(.-)%*%)")
             table.insert(types[current_type_name].fields, {
               name = field_name,
               type = field_type or "unknown",
+              comment = field_comment,
             })
           end
         end
@@ -254,10 +256,12 @@ local function parse_db_file(content)
       local field_name = line:match("^%s*(%w+)%s*:")
       if field_name then
         local field_type = line:match(":%s*([%w_]+)")
+        local field_comment = line:match("//%s*(.+)$") or line:match("%(%*(.-)%*%)")
         if field_type then
           table.insert(types[current_type_name].fields, {
             name = field_name,
             type = field_type,
+            comment = field_comment,
           })
         end
       end