Teach release planner to update generated Node loader diagnostics

The v0.26.1 release planner updated the generated Node loader version comparisons but left the diagnostic literals at `expected 0.26.0` in the Discovery, Evidence, Relay, and BReg loaders.

The release PR corrected the generated output directly. Update the planner rewrite for `generated-binding-loader` files and add a focused regression assertion that the enforced version and reported expected version stay aligned.

This is follow-up tooling hardening and is not a v0.26.1 release blocker.

Start with the release planner rewrite for generated-binding-loader files and inspect how it updates version comparisons and diagnostic literals. Add a focused regression assertion covering the Discovery, Evidence, Relay, and BReg loaders, and verify that the enforced version and reported expected version remain aligned.

Written by the indexing model from the issue text.