PiUI style mobile terminal adaptation

Key features

• PiUI page turnerWhen ≤768px, the three-column frame is rearranged into a two-page horizontal snap track - the sidebar page is half-width (about half the viewport), and the chat page is full-width
• InitialThe sidebar is half open and permanent (flat page on the left + chat card on the right half)
• The root slot of dsh is the single slot built into the framework, which is exclusively occupied by ui-layout - plug-ins cannot replace AppFrame (single slot already has a registration will directly throw an error)
• DSHFind — DeepSeek Harness plug-in market and learning community
• When sliding to the sidebar page, the chat card is exposed on the right half (half information flow), the same structure of PiUI