tools: SEAMS fix-command (Debug) vs CI check (Release) configuration coupling — align properly

[genwave-radio]

⚙️ What

CONTRIBUTING's documented fix command (dotnet run --project tools/SeamIndexGenerator) builds Debug; the CI drift check runs Release. Outputs are byte-identical today (verified: zero configuration-conditional code in the solution) — but the coupling is invisible, and a future #if DEBUG/conditional registration would make the documented command write a file the check rejects.

🎯 Proper fix (pick at build time)

1. Pin both to one configuration: the script and the CONTRIBUTING command both say --configuration Release; or
2. A guard: the drift check generates in BOTH configurations and asserts they match (turns the invariant into a red check instead of a convention) — costs one extra build in CI.
   Option 2 is the fitness-suite-flavored answer; option 1 is the cheap one.

📎 Origin: T217 review note 5 (2026-08-07); Dean: "would like to fix properly, eventually."