test(adapter-openclaw): split DKG channel test suite

[branarakic]

Summary

• split the 4k-line adapter-openclaw DKG channel test into 13 part files
• preserve the original test bodies and shared per-file setup while keeping each generated file under 500 lines

Verification

• compared ordered test titles between the original file and split files
• built @origintrail-official/dkg-core in the worktree for local resolution
• ../../node_modules/.bin/vitest run --passWithNoTests test/dkg-channel.part-*.test.ts

[github-actions]

Codex review skipped: filtered diff is 9927 lines (cap: 5,000). Please consider splitting this into smaller PRs for reviewability.