Add dynamic ZCU and ZPPI shadow foundations

[the-code-learner]

Scope

Implements the first Protocol Economics P1 tranche from the 19 August 2026 working paper while keeping all monetary effects in shadow mode.

Changes

• add dynamic per-work-class ZCU reference snapshots from verified compute-slot evidence;
• weight slot observations by delivered slot time, availability EWMA, success EWMA and confidence;
• use deterministic weighted medians, EWMA smoothing and bounded per-epoch reference movement;
• add a ZPPI price-relative basket for compute, data availability and storage with coverage/reliability gates;
• encode the exact annual target implied by a 2% purchasing-power decline: 1 / 0.98 ~= 1.020408163;
• update docs/tokenomics-v2.md so purchasing power, not fixed supply growth, is the normative monetary objective;
• keep the existing supply-growth evaluator as a legacy shadow simulation boundary until ZPPI is integrated end-to-end.

Safety boundary

No live ZPH minting, fee split, reward routing, levy or supply mutation is activated by this change. Thin or unauthenticated economic evidence fails closed.

Next P1 tranche

Dormancy histogram, productive-coverage hooks, capital-lineage metadata and fragmentation-cost simulation.