[release] Prune ~70 stale remote branches

[cursor]

Owner squad: @THOClabs/release-engineering · Priority: P3 · Area: release

Problem

The remote has ~70 branches, many near-duplicate (feat/neo-*, hourly-scan-*, feature/*, nightwatch/*). This obscures the true state of work and makes it hard to tell what is merged vs. abandoned.

Acceptance criteria

• Identify which branches are merged or superseded.
• Delete merged/stale branches (keep main + any genuinely active work).
• Adopt a branch-naming + cleanup convention (document in CONTRIBUTING.md).

Evidence

docs/reviews/2026-06-23-holistic-review.md §5.