fix: correct inverted balance/min_base values in OPG insufficient-balance error

[amathxbt]

🐛 Bug: Misleading Error Message in ensure_opg_approval

File: src/opengradient/client/opg_token.py — ensure_opg_approval()

What's broken

On line 207, when the wallet balance is below the minimum required allowance, the error message displays the two values in the wrong order:

# Condition (L205): min_base > balance  →  balance < min_base
elif min_base > balance:
    raise ValueError(
        f"Wallet {owner} has less OPG tokens than the minimum allowance ({min_base} < {balance}). "
        #                                                                  ^^^^^^^^^^^^^^^^^^^^^^
        #                                                         WRONG: min_base < balance is False!

The printed comparison (min_base < {balance}) is logically inverted — the condition fires precisely when min_base > balance, so printing min_base < balance shows a false statement and confuses debugging.

Fix

Replace with a clear, accurate message that shows actual wallet balance vs. requirement:

raise ValueError(
    f"Wallet {owner} has insufficient OPG balance: "
    f"has {balance / 10**18:.6f} OPG, "
    f"but the minimum required is {min_base / 10**18:.6f} OPG. "
    f"Fund the wallet before approving."
)

Impact

Users encountering this error while debugging a low-balance issue would see a backwards comparison like (1000000000000000000 < 500000000000000000) — which appears to say they have more than enough, when they actually don't. This causes significant confusion and wasted debugging time.

Files Changed

• src/opengradient/client/opg_token.py

[amathxbt]

@adambalogh