BaseStrategy: harvest, tend, and the Realize-Report-Reinvest Cycle

What You Are Building

The strategy-side counterpart to the vault's report(). StrategyHarvest extends BaseStrategy (section 8) and adds the periodic cycle that closes the loop between strategy state and vault accounting:

1. Read what the vault wants back.
2. Realize the strategy's P&L.
3. Call vault.report() to settle.
4. Reinvest whatever underlying is left in the strategy.

The keeper bot calls harvest() on a cadence picked by the strategist via harvestTrigger(). Yearn keepers across mainnet harvest strategies many times per day.