ci: add check-sensitive pre-merge gate

Hand-written change from the internal SDK repository. The original commit
message is intentionally not mirrored; see the source repository for details.

Sync-Source-Commit: 0cffa769b5ac73c86d54da5a6009a79110f9f8c4
Hand-Written-Reason: No Ark-APIs provenance marker; treated as a hand-written source commit.
Release-Version: 0.7.0

Author: ark-hand[bot]

examples/self_hosted_mcp_worker/README.md

@@ -1,6 +1,6 @@
 # Self-hosted MCP worker
 
-This example follows Anthropic's client-side MCP helper example at the same
+This example follows the client-side MCP helper pattern at the same
 level of abstraction: connect to an MCP server, discover its tools, convert
 them, and run an existing self-hosted Environment Worker.