fix(nvim): eliminate \r corruption in buffer mutations

- Pre-process and strip carriage returns natively in Rust before RPC serialization.

- Pass replacement strings to Neovim as native MsgPack arrays to bypass Lua vim.split overhead.

- Directly feed table arrays into vim.api.nvim_buf_set_lines for exact buffer matches.

nvim-core/src/lib.rs

@@ -1326,7 +1326,14 @@ pub async fn run_mcp_loop(app_name: &str, app_version: &str) {
                                 )
                             }
                             "edit" => {
-                                let args_rmp = json_to_rmpv(args);
+                                let mut modified_args = args.clone();
+                                if let Some(content) = modified_args.get_mut("replacement_content") {
+                                    if let Some(s) = content.as_str() {
+                                        let lines: Vec<String> = s.split('\n').map(|l| l.trim_end_matches('\r').to_string()).collect();
+                                        *content = serde_json::json!(lines);
+                                    }
+                                }
+                                let args_rmp = json_to_rmpv(&modified_args);
                                 let code = "
                                     local args = ...
                                     local file = args.file
@@ -1341,8 +1348,8 @@ pub async fn run_mcp_loop(app_name: &str, app_version: &str) {
                                     if not end_line then
                                         error(\"Missing 'end_line'\")
                                     end
-                                    local content = args.replacement_content
+                                    local content_lines = args.replacement_content
-                                    if not content or content == vim.NIL then
+                                    if not content_lines or content_lines == vim.NIL then
                                         error(\"Missing 'replacement_content'\")
                                     end
                                     
@@ -1351,8 +1358,7 @@ pub async fn run_mcp_loop(app_name: &str, app_version: &str) {
                                         vim.fn.bufload(bufnr)
                                     end
                                     
-                                    local lines = vim.split(content, '\\n', { plain = true })
+                                    vim.api.nvim_buf_set_lines(bufnr, start_line - 1, end_line, false, content_lines)
-                                    vim.api.nvim_buf_set_lines(bufnr, start_line - 1, end_line, false, lines)
                                     
                                     local win = vim.fn.bufwinid(bufnr)
                                     if win ~= -1 then
@@ -1398,7 +1404,14 @@ pub async fn run_mcp_loop(app_name: &str, app_version: &str) {
                                 )
                             }
                             "create_scratch" | "open_buffer" => {
-                                let args_rmp = json_to_rmpv(args);
+                                let mut modified_args = args.clone();
+                                if let Some(content) = modified_args.get_mut("content") {
+                                    if let Some(s) = content.as_str() {
+                                        let lines: Vec<String> = s.split('\n').map(|l| l.trim_end_matches('\r').to_string()).collect();
+                                        *content = serde_json::json!(lines);
+                                    }
+                                }
+                                let args_rmp = json_to_rmpv(&modified_args);
                                 let code = "
                                     local args = ...
                                     local name = (args.name and args.name ~= '') and args.name or '[Antigravity Scratch]'
@@ -1408,8 +1421,7 @@ pub async fn run_mcp_loop(app_name: &str, app_version: &str) {
                                     vim.bo[buf].buftype = 'nofile'
                                     vim.bo[buf].bufhidden = 'hide'
                                     if args.content then
-                                        local lines = vim.split(args.content, '\\n')
+                                        vim.api.nvim_buf_set_lines(buf, 0, -1, false, args.content)
-                                        vim.api.nvim_buf_set_lines(buf, 0, -1, false, lines)
                                     end
                                     if args.filetype and args.filetype ~= '' then
                                         vim.bo[buf].filetype = args.filetype