feat(Codegen): native Solidity panic payload emission (Panic(uint256))

[Th0rgal]

Promoted from #1982 P2 to a standalone tracked issue (was previously only a roadmap bullet).

Problem

Solidity panic revert payloads (Panic(uint256) selector 0x4e487b71 + code) are modeled via the small solidityPanicModule ECM (Morpho Midnight Contract.lean:1765, Th0rgal/morpho-verity).

Goal

Compiler-owned panic payload emission (and the matching proof-side revert observable), removing the ECM. Natural to bundle with checked-arithmetic emission (#1993), which needs panic(0x11) paths, and adjacent to the revertError non-literal-args work (#1974).