P3 tokenomics: emission schedule, MAX_SUPPLY, fee denomination, and burn policy

[umeradl]

Part of the P3 mechanism-design push (tracking issue #36). Design context: MECHANISM_DESIGN §7–§8, implementation issues #42 (tokenomics) and #43 (fees/treasury).

cc @abrahamnash — these set the token's long-term economics, and the white paper (§8) already stakes out positions we should either follow or consciously diverge from.

1. Emission schedule shape and MAX_SUPPLY

The white paper describes inflation-funded staking rewards with an Ethereum-2-style decreasing rate plus fee-funded burn. Current proposal: a per-GI reward subsidy on geometric decay per epoch, a hard MAX_SUPPLY cap, and an inflation guard (per-GI mint ceiling), with mints triggered only by GI lifecycle events. Emission tops up model-owner reward pools during bootstrap and decays to zero as fees take over. Open: decay rate, epoch length, and the actual MAX_SUPPLY number — to be grounded in the P3-5.2 simulation (stable validator income at target / 10× / 0.1× participation).

2. Fee denomination: DIN-only or dual-asset?

Registration fees are ETH today; staking and rewards are DIN. Recommendation: converge on DIN for all protocol fees in 2.0 — single-asset accounting, reinforces token utility, and the depositAndMint on-ramp makes acquisition trivial on devnet. Keeping ETH fees means the fee router handles both assets for no devnet benefit. Migration: DIN-denominated params added alongside, ETH fees deprecated after one release.

3. depositAndMint cap or retirement

DinCoordinator.depositAndMint (ETH → DIN at a fixed admin-set rate) is effectively an unlimited mint — fine as a devnet faucet, not fine on any real-value network, and it will be flagged in audit. When do we cap it, and what replaces it as the on-ramp?

4. Burn policy

Proposed sinks: the slashed-stake burn share (see the slashing-economics discussion) plus an optional fraction of protocol fees burned — starting at 0% with the hook kept. The white paper also earmarks a share of network fees for public-goods funding (quadratic funding); do we reserve a routing slot for that now alongside {validatorPool, treasury, burn, storage}?

[umeradl]

Thanks, Abraham, for the thorough answers here — we're wiring these into the DIN P3 specs now.