chore: bump Motoko to v1.7.0

[github-actions]

Summary

Automated bump of .sources/motoko from v1.6.0 to v1.7.0.

• Ran npm run sync:motoko — synced docs from the new release
• Build passed ✓

⚠️ Warnings — manual review required

• FILE-EMBED EMPTY: ../examples/todo-error.mo#L60-L60 in docs/languages/motoko/fundamentals/error-handling.md — line range resolved to empty content (upstream off-by-one?)

Checklist

• Review synced content for breaking changes
• Check release notes for API or syntax changes that affect hand-written docs
• Verify any new sections or renamed files are handled correctly

Sync recommendation

sync from caffeinelabs/motoko doc/md

[marc0olo]

Closing this PR — it was created by the workflow using GITHUB_TOKEN with elevated permissions, which is not allowed now that the repo is public.

The fix is tracked in #196: we're switching to the pr-automation-bot-public GitHub App for automated PR creation. Once those changes are merged, we'll re-trigger the workflow manually to re-run the same Motoko v1.7.0 sync via the new setup.