Governance 17: update PoC model lineup

Original Proposal Text

Set delegation initial_model_id to MiniMaxAI/MiniMax-M2.7, keep only MiniMaxAI/MiniMax-M2.7 in PoC params, remove Qwen/Qwen3-235B-A22B-Instruct-2507-FP8, moonshotai/Kimi-K2.6 from PoC params, and delete Qwen/Qwen3-235B-A22B-Instruct-2507-FP8, moonshotai/Kimi-K2.6 from governance models. Parameters: epoch_params: [object Object] validation_params: [object Object] poc_params: [object Object] tokenomics_params: [object Object] collateral_params: [object Object] bitcoin_reward_params: [object Object] dynamic_pricing_params: [object Object] bandwidth_limits_params: [object Object] confirmation_poc_params: [object Object] genesis_guardian_params: [object Object] developer_access_params: [object Object] participant_access_params: [object Object] transfer_agent_access_params: [object Object] devshard_escrow_params: [object Object] fee_params: [object Object] delegation_params: [object Object]