feat: New letta.md system prompt + source-faithful benchmarking prompts [LET-7747, LET-7787] (#1313)

Co-authored-by: Letta <noreply@letta.com>

src/cli/App.tsx

@@ -3143,10 +3143,7 @@ export default function App({
               const normalize = (s: string) => {
                 // Match prompt presets even if memfs addon is enabled/disabled.
                 // The memfs addon is appended to the stored agent.system prompt.
-                const withoutMemfs = s.replace(
-                  /\n## Memory Filesystem[\s\S]*?(?=\n# |$)/,
-                  "",
-                );
+                const withoutMemfs = s.replace(/\n# Memory[\s\S]*$/, "");
                 return withoutMemfs.replace(/\r\n/g, "\n").trim();
               };
               const sysNorm = normalize(agentSystem);