resource_link content blocks are silently dropped from tool output

[dhruvkej9]

Problem

_extract_content_parts only reads text/data attributes from content blocks. A resource_link block carries neither — only uri/name — so it is dropped silently from non---json output.

Reproduction

Minimal stdio MCP server with a tool returning:

{"content": [
  {"type": "text", "text": "see:"},
  {"type": "resource_link", "uri": "probe://linked", "name": "linked-doc", "mimeType": "text/plain"}
]}

$ mcp2cli --mcp-stdio "python server.py" with-link
see:

The link is gone. Verified against v3.5.0 (commit 6b8ae5f).

Expected

see:
linked-doc: probe://linked

(--json is unaffected — it dumps the full envelope.)