Manage the active goal-mode objective.

Use a single op field:

• create starts a goal. Requires objective; optional token_budget must be positive. Use only when no goal exists and no goal is paused.
• get returns the current goal (active or paused) and remaining token budget.
• resume re-activates a paused goal so work can continue.
• complete marks the goal complete after you have verified every deliverable against current evidence.
• drop discards the current goal without completing it.

Examples:

• goal({"op":"create","objective":"Implement feature X","token_budget":50000})
• goal({"op":"get"})
• goal({"op":"resume"})
• goal({"op":"complete"})
• goal({"op":"drop"})

Do not call complete because a budget is low or a turn is ending. Call it only when the goal is actually done and verified. If get shows a paused goal, call resume before continuing work on it.