alpha: restore transformERC20 clear-signing with certified semantics

[BitHighlander]

Goal

Restore normal-mode 0x transformERC20 swaps on alpha without trusting an undisclosed transformations[] tail. The 7.14.2 release intentionally routes selector 0x415565b0 through AdvancedMode.

Required design

• Parse the complete canonical ABI with overflow-safe bounds checks: the 0xa0 array offset, count, every tuple offset, uint32 nonce, bytes length/padding, and any explicitly supported attribution suffix.
• Bind the complete calldata hash, chain ID, Exchange Proxy address, selector, decoded economic fields, and approved transformer policy/version to device-verifiable signed metadata. Missing, expired, mismatched, or unknown metadata must fall back to AdvancedMode.
• Display protocol, exact input asset/amount, minimum receive asset/amount, signer-as-recipient, and attached native value.
• Reject UINT256_MAX input, zero minimum receive, ERC-20 input with attached ETH, and native input where msg.value does not equal the displayed input.
• Reject a second EthereumSignTx while calldata is pending, before any confirmation screen.
• Keep standard ERC-20 transfer/approve and the separate sellToUniswap handler independent.

Acceptance tests

• Valid certified quote clear-signs on every supported chain/address pair.
• Same static head with different transformation tails has different calldata hashes and cannot reuse the same certificate.
• Noncanonical offsets, overlap, dirty narrow values, truncation, oversized lengths, padding/trailing-data ambiguity, max input, zero minimum, and value mismatches fail closed.
• Streamed calldata, cancellation, unexpected ACK, and second initialization leave no active signer state.
• Vault and firmware version gates agree: stable 7.14.2 uses AdvancedMode; alpha enables normal review only when the certified path is available.

Contract tests against a pinned 0x source are supporting evidence, not the trust boundary: the 0x owner can change the trusted transformer deployer. The signed policy must make that external trust explicit and revocable.