Prop 278: Decommission stDYM

Signaling proposal to decommission stDYM (liquid staked DYM): liquid staking of DYM is disabled on July 1, 2026; existing stDYM holders may redeem through the standard redemption process during a grace period ending September 1, 2026, after which redemptions are permanently disabled.

Full proposal text and discussion: https://common.xyz/stride/discussion/1312763-proposal-deprecate-chains-umee-stargaze-evmos-and-decommission-stdym