feat(Semantics): first-class multicall + delegatecall frame semantics (bytes[] iteration)

Promoted from #1982 P1 to a standalone tracked issue (was previously only a roadmap bullet).

Problem

multicall(bytes[]) with self-delegatecall is currently a giant hand-rolled ECM: manual calldata length/offset walking via raw YulStmt, delegatecall, returndatacopy, revert bubbling, plus a delegatecall-context axiom (Morpho Midnight Contract.lean:22–95, Th0rgal/morpho-verity). Low-level delegatecall exists but is tracked under notModeledProxyUpgradeability.

Goal

• bytes[] calldata iteration support (depends on the dynamic ABI codec, #1982 P0-1).
• A source-level multicall helper with proven revert-bubbling semantics.
• Delegatecall-with-own-storage-context semantics for the self-delegatecall case (narrower and sounder than general proxy upgradeability), replacing the per-contract context axiom.

Acceptance

Midnight multicall expressible as a standard helper; the delegatecall-context axiom and raw YulStmt introspection removed from the trust report.

Start with the dynamic ABI codec work in #1982 and the delegatecall-context discussion in Morpho Midnight Contract.lean:22–95. Review the existing raw YulStmt multicall handling and trust report; done means bytes[] iteration, source-level multicall with proven revert bubbling, and removal of the delegatecall-context axiom and raw YulStmt introspection.