[stage2] fix: serialize multiline descriptions in legacy TOML renderer (#2097)

* fix: preserve multiline descriptions in legacy toml renderer

* refactor: reuse toml escape helper for prompt fallback

src/specify_cli/agents.py

@@ -191,8 +191,9 @@ class CommandRegistrar:
         toml_lines = []
 
         if "description" in frontmatter:
-            desc = frontmatter["description"].replace('"', '\\"')
-            toml_lines.append(f'description = "{desc}"')
+            toml_lines.append(
+                f'description = {self._render_basic_toml_string(frontmatter["description"])}'
+            )
             toml_lines.append("")
 
         toml_lines.append(f"# Source: {source_id}")
@@ -209,17 +210,22 @@ class CommandRegistrar:
             toml_lines.append(body)
             toml_lines.append("'''")
         else:
-            escaped_body = (
-                body.replace("\\", "\\\\")
-                .replace('"', '\\"')
-                .replace("\n", "\\n")
-                .replace("\r", "\\r")
-                .replace("\t", "\\t")
-            )
-            toml_lines.append(f'prompt = "{escaped_body}"')
+            toml_lines.append(f"prompt = {self._render_basic_toml_string(body)}")
 
         return "\n".join(toml_lines)
 
+    @staticmethod
+    def _render_basic_toml_string(value: str) -> str:
+        """Render *value* as a TOML basic string literal."""
+        escaped = (
+            value.replace("\\", "\\\\")
+            .replace('"', '\\"')
+            .replace("\n", "\\n")
+            .replace("\r", "\\r")
+            .replace("\t", "\\t")
+        )
+        return f'"{escaped}"'
+
     def render_skill_command(
         self,
         agent_name: str,

tests/test_extensions.py

@@ -13,6 +13,7 @@ import pytest
 import json
 import tempfile
 import shutil
+import tomllib
 from pathlib import Path
 from datetime import datetime, timezone
 
@@ -1014,6 +1015,21 @@ $ARGUMENTS
         assert "\\n" in output
         assert "\\\"\\\"\\\"" in output
 
+    def test_render_toml_command_preserves_multiline_description(self):
+        """Multiline descriptions should render as parseable TOML with preserved semantics."""
+        from specify_cli.agents import CommandRegistrar as AgentCommandRegistrar
+
+        registrar = AgentCommandRegistrar()
+        output = registrar.render_toml_command(
+            {"description": "first line\nsecond line\n"},
+            "body",
+            "extension:test-ext",
+        )
+
+        parsed = tomllib.loads(output)
+
+        assert parsed["description"] == "first line\nsecond line\n"
+
     def test_register_commands_for_claude(self, extension_dir, project_dir):
         """Test registering commands for Claude agent."""
         # Create .claude directory