What is the juristic classification of the aforementioned partnership contract, and does the contracting partner guarantee delays in project delivery, or does he only guarantee in cases of transgression and negligence?

The aforementioned company is a partnership (Sharikat al-Inan), which is permissible by consensus, as mentioned by Ibn al-Mundhir. A partnership is based on agency (wakalah) and trust (amanah), where each partner authorizes the other to act with the shared capital. As for a partner undertaking to complete a task for the company, this is an independent contract, and the partner is held accountable for their shortcomings in it just like an outsider.