Drop the nodespace/gate commit status; no branch protection #3089

Problem

bun run merge records a nodespace/gate commit status, and CLAUDE.md, ADR-047 and the development docs state that main requires it. Branch protection was never enabled, and on reflection it isn't wanted: the goal is deterministic testing that doesn't choke parallel worktree work, not a GitHub-enforced receipt. The status is bookkeeping with no consumer, and the docs describe an enforcement that doesn't exist.

Solution

• Remove the commit-status posting from scripts/merge-pr.ts (keep --match-head-commit)
• Remove "main requires nodespace/gate" wording from CLAUDE.md and nodespace-docs (ADR-047 amendment, overview, pr-review, testing-guide); bun run merge stays the documented merge path, as a convention

Acceptance criteria

• bun run merge no longer calls the statuses API
• No doc or CLAUDE.md claims main requires a status check