Spec: Arena v2 product primitives (timers, CRED, prizes, XP)

Context

Authoritative product spec for Arena v2. Parent epic: #238 (closed).

Replace docs/product/primitives.md launchpad semantics with TimeArena rules.

Document these timer rules:

Podium	Initial timer	Extension on buy	Hard-reset if remaining below	Reset to
Last Buy (primary)	24h	+120s	13m	15m
Streak	18h	+90s (+1.5m)	8.5m	10m
Time Booster	12h	+60s (+1m)	4m	5m
WarBow	48h	+300s (+5m)	55m	1h

Each podium has independent deadline + epoch counter; epochs are not synchronized
CHARM: fixed 1000 DOUB / CHARM (admin-settable); min/max CHARM band unchanged in spirit
Buy economics: 10% DOUB → each podium pool; 7.5% DOUB → each podium next-round seed; 30% → admin sell vault; 70% total to prizes
Play CRED: non-transferable; 70 CRED = one free buy (min/max CHARM band applies); admin + optional grantor contract can mint
CRED yield: each buy mints 35 CRED split pro-rata to current-epoch CHARM holders
Last Buy epoch: CHARM tracked per epoch; on Last Buy reset → claim pending CRED, zero epoch CHARM onchain
XP: linear 1–10 from min→max buy; L1=20 XP; +5 XP per level requirement until 100 XP/level cap, then flat 100 XP/level forever
WarBow PvP: steal/guard/revenge/flag; costs 1000 / 10000 / 1000 / 50000 DOUB; WarBow scores reset when WarBow timer epoch ends; indexer retains historical epochs for admin finalize
Referrals: existing codes preserved; 5% CRED to referrer + 5% CRED to buyer (not CHARM)

Revenge DOUB cost — default 1000 (same as steal)
Referral registration burn — keep 1 CL8Y for existing-code continuity vs migrate to DOUB
CRED referral 5% basis — 5% of the 35 CRED mint per side
Podium settlement trigger — permissionless rollPodiumEpoch(cat) vs auto on first post-expiry buy
Route naming — /arena primary with /timecurve redirect (optional)