fix: morpho withdraw action dynamically fetches token decimals instead of hardcoding 18

[furkankoykiran]

Summary

Fixes #946

MorphoActionProvider.withdraw() used Web3.to_wei(assets, "ether") to convert the assets input to atomic units, which hardcodes 18 decimals regardless of the actual token's decimals. This produces incorrect amounts for any token that isn't 18 decimals (e.g., USDC with 6 decimals).

Example: Withdrawing 100 USDC (6 decimals) from a Morpho vault:

• Expected atomic amount: 100 * 10^6 = 100_000_000
• Actual (buggy) atomic amount: 100 * 10^18 = 100_000_000_000_000_000_000 (12 orders of magnitude too large)

Changes

schemas.py

• Added token_address field to MorphoWithdrawSchema (matching MorphoDepositSchema)
• Changed assets description from "atomic units" to "whole units" to match the actual behavior

morpho_action_provider.py

• Replaced Web3.to_wei(assets, "ether") with dynamic decimal lookup via wallet_provider.read_contract(), matching the existing deposit() implementation
• Updated withdraw action description to include token_address, examples, and important notes (consistent with deposit)

test_morpho_action_provider.py

• Updated all withdraw tests to include token_address in args and mock read_contract
• Added test_morpho_withdraw_non_18_decimal_token to verify correct behavior with 6-decimal tokens (USDC)

changelog.d/946.bugfix.md

• Added towncrier changelog entry

Testing

All 13 Morpho tests pass:

13 passed, 9 warnings in 7.88s

[cb-heimdall]

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