Extend the existing Pi bundle-MCP Docker e2e harness so the live stdio MCP
probe also exercises `splitSdkTools` and asserts the configured server tool
reaches `customTools` for coding/messaging and is filtered out for minimal
and `tools.deny: ["bundle-mcp"]`. The harness already had real materialize
plus profile-filter coverage against a real stdio MCP child, but did not
assert the splitSdkTools().customTools boundary, which is the value the SDK
serializes to the outbound provider request body and the disputed boundary
on #76063.
Refs #76063.
