release: v0.22.7

[jdogresorg]

Patch train v0.22.7 for xchain-node: the version bump, the v0.22.7 release manifest, and one dependency override.

• Manifest: moves only the xchain-hub pin, to its signed v0.22.7 master merge commit (52d1067d). Every other pin and the trainActivation block are identical to v0.22.6. Release-management section 7.
• Dependency: overrides @modelcontextprotocol/sdk (pulled in through @dankest-llc/xchain-sdk at ^1.29.0) to ^1.31.0, which resolves 1.32.1 and clears the high advisory GHSA-6qxp-vccf-f47h. npm audit --omit=dev --audit-level=high exits 0 on this branch; it read the advisory on 1.30.0 before.

Code structure clean; ci-gate: PASS xchain-node 3109 pass / 0 fail.