Test buffered modes for request/response

[evaline-ju]

Test description

Following tool response checking in #18 , there were a few observed edge cases for particular tools (e.g. test3_get_weather) where expected MCP errors were only surfaced intermittently instead of consistently, despite the plugin and nemo check server surfacing expected messages to "block" in logs.

We would like to first answer:

• Can we avoid chunk edge cases and buffering within the ext-proc server itself by updating https://github.com/kagenti/plugins-adapter/blob/main/filter.yaml#L31-L32 from STREAMED to BUFFERED?
• Do we need to update the ext-proc server implementation if the modes are updated?

We will open bugs based on this investigation.

[evaline-ju]

See if issue of intermittent chunks returning is persistent

example:

curl -i http://mcp.127-0-0-1.sslip.io:8001/mcp \
-H "Content-Type: application/json" \
-d '{ "jsonrpc": "2.0", "id": 1, "method": "initialize" }'


curl -X POST http://mcp.127-0-0-1.sslip.io:8001/mcp \
  -H "Content-Type: application/json" \
  -H "Accept: text/event-stream, application/json" \
  -H "Mcp-Session-Id: REPLACE-SESSION-ID-HERE" \
  -d '{
    "jsonrpc": "2.0",
    "id": 1,
    "method": "tools/call",
    "params": {
      "name": "test3_get_weather",
      "arguments": {
        "city": "my password is secret"
      }
    }
  }'
event: message
data: {"jsonrpc":"2.0","id":1,"result":{"content":[{"type":"text","text":"{\"city\":\"my password is secret\",\"temperature\":\"72F\",\"forecast\":\"Sunny\"}"}],"structuredContent":{"city":"my password is secret","temperature":"72F","forecast":"Sunny"},"isError":false}}

curl: (18) transfer closed with outstanding read data remaining

[mvle]

Tested with BUFFERED in filter.yaml. Seems to work w/o any changes to plugin adapter server code. Tested with:
test3_get_weather, test2_hello_world, everything_getTinyImage, everything_longRunningOperation, test3_time, test3_slow