fix: Change memory server default filename from memory.json to memory.jsonl

The Memory MCP server uses JSONL format (JSON Lines) where each line
contains a separate JSON object, but was using a .json file extension.
This caused IDE lint errors and confusion since the file is not valid JSON.

Changes:
- Update default filename in index.ts from memory.json to memory.jsonl
- Update documentation references in README.md
- Maintain backward compatibility for existing MEMORY_FILE_PATH configs

Fixes #2361

Co-authored-by: Ola Hungerford <olaservo@users.noreply.github.com>

src/memory/README.md

@@ -173,14 +173,14 @@ The server can be configured using the following environment variables:
         "@modelcontextprotocol/server-memory"
       ],
       "env": {
-        "MEMORY_FILE_PATH": "/path/to/custom/memory.json"
+        "MEMORY_FILE_PATH": "/path/to/custom/memory.jsonl"
       }
     }
   }
 }
 ```
 
-- `MEMORY_FILE_PATH`: Path to the memory storage JSON file (default: `memory.json` in the server directory)
+- `MEMORY_FILE_PATH`: Path to the memory storage JSONL file (default: `memory.jsonl` in the server directory)
 
 # VS Code Installation Instructions