Project context for Tasks

Projects can now carry the context that should be present whenever work starts there.

Add the shared intent, architecture, and constraints alongside the Project name and repository. When a Task runs, Alloyqa places that context before the Task-specific instructions, while keeping the Task requirements authoritative if they conflict.

Decisions stay attached to the work instead of being copied into every Task. The context is bounded and does not replace Task instructions or retrieve unrelated Project history.