ethena_stake / ethena_cooldown_start / ethena_unstake
        ↓  returns tx dict  {to, data, value, chain_id}
wallet_sign_transaction(tx)          ← wallet skill
        ↓  returns signed_tx hex
wallet_sign_transaction broadcast    ← same call, auto-broadcasts

Step 1  ethena_rate()                    # confirm rate + cooldown before tx
Step 2  ethena_stake("100", receiver)    # returns [approve_tx, deposit_tx]
Step 3  wallet_sign_transaction(approve_tx, broadcast=True)
Step 4  wallet_sign_transaction(deposit_tx, broadcast=True)

Step 1  ethena_rate()                    # get live cooldown duration
Step 2  ethena_cooldown_start("100")     # returns cooldown_tx
Step 3  wallet_sign_transaction(cooldown_tx, broadcast=True)
Step 4  [wait cooldown_hours]
Step 5  ethena_unstake(receiver)         # returns unstake_tx
Step 6  wallet_sign_transaction(unstake_tx, broadcast=True)

IF "APY" OR "yield" OR "return" OR "收益率" OR "年化"
  → ethena_apy()

IF "rate" OR "price" OR "how much USDe per sUSDe" OR "汇率" OR "多少USDe"
  → ethena_rate()

IF "balance" OR "how much do I have" OR "余额"
  → ethena_balance(wallet_address)

IF "stake" OR "deposit" OR "质押" AND amount given
  → ethena_stake(amount, receiver)

IF "unstake" OR "redeem" OR "cooldown" OR "withdraw" OR "赎回" — starting flow
  → ethena_cooldown_start(amount)

IF "claim" OR "unstake" OR "withdraw" AND cooldown already done
  → ethena_unstake(receiver)

IF "how long" OR "cooldown duration" OR "等多久"
  → ethena_rate()  ← returns cooldown_seconds live from chain

ethena_apy()
→ "当前 APY 3.72%，7日均值 3.68%"

ethena_rate()
→ "1 sUSDe = 1.227675 USDe（totalAssets/totalSupply 实时计算）"

ethena_balance("0x...")
→ {usde_balance: 500.0, susde_balance: 81.46, susde_in_usde: 100.0}

ethena_rate()          # get live rate for estimate
ethena_stake("100", receiver="0x...")
→ [{approve tx}, {deposit tx}]  # execute in order

ethena_rate()                                   # Step 1: confirm rate
ethena_stake("100", receiver="0x...")           # Step 2: get calldata
→ [approve_tx, deposit_tx]
wallet_sign_transaction(approve_tx, broadcast=True)   # Step 3
wallet_sign_transaction(deposit_tx, broadcast=True)   # Step 4
→ tx_hash confirmed

ethena_rate()                                         # Step 1: get cooldown
ethena_cooldown_start("50")                           # Step 2: get calldata
→ {cooldown_tx, cooldown_hours: 24.0}
wallet_sign_transaction(cooldown_tx, broadcast=True)  # Step 3
→ tx_hash confirmed, 等待 24h 后再调 ethena_unstake

ethena_rate()
→ "cooldown_seconds: 86400 → 当前需等待 24 小时"

ethena_cooldown_start("50")
→ {transaction: {...}, cooldown_hours: 24.0}

ethena_unstake("0x...")
→ {transaction: {...}}

ethena_apy()
→ "Current APY: 3.72%"