docs: Update Task 0.4 to use fast sub-agents for middle context chunk summarization rather than blind deletion

docs: Add task 0.4 Prerequisite (Head and Tail Context Truncation)

docs: Add task 0.1, 0.2 and 0.3 Prerequisite Swarm Upgrades (Skill Binding, Lock UI)

docs: Harness Engineering Design, Execution, and Test plans