Fix MDX parsing error and update card images (#3213)

* Fix MDX parsing error and add broken link CI check

Escape curly braces in docstring example that broke MDX parsing,
update card images, and add docs broken link check to CI.

* Revert CI broken link check — Mintlify runs this already

* Use code fence instead of inline backticks for MDX escaping

* chore: Update SDK documentation

---------

Co-authored-by: marvin-context-protocol[bot] <225465937+marvin-context-protocol[bot]@users.noreply.github.com>

docs/python-sdk/fastmcp-cli-client.mdx

@@ -102,13 +102,15 @@ or nested arguments.
 
 **Examples:**
 
+```
 fastmcp call server.py greet name=World
 fastmcp call server.py resource://docs/readme
 fastmcp call server.py analyze --prompt data='[1,2,3]'
 fastmcp call http://server/mcp create --input-json '{"tags": ["a","b"]}'
+```
 
 
-### `discover_command` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/cli/client.py#L875" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+### `discover_command` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/cli/client.py#L877" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 discover_command() -> None

src/fastmcp/cli/client.py

@@ -838,10 +838,12 @@ async def call_command(
     or nested arguments.
 
     Examples:
+        ```
         fastmcp call server.py greet name=World
         fastmcp call server.py resource://docs/readme
         fastmcp call server.py analyze --prompt data='[1,2,3]'
         fastmcp call http://server/mcp create --input-json '{"tags": ["a","b"]}'
+        ```
     """
 
     if not target: