feat(Events): broaden source-shaped emit surface (dynamic/struct event args)

[Th0rgal]

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

Problem

Scalar events are built-in and proven, but many EventsLib-style events with dynamic (bytes) or struct arguments are still not source-shaped emit in downstream ports (Morpho Blue/Midnight), leaving event fidelity gaps in otherwise line-faithful functions.

Goal

Extend the event surface to dynamic/struct arguments — the encoder half of the dynamic ABI codec (#1982 P0-1) — with ABI-shaped log payload proofs and smoke coverage.

[Th0rgal]

Event-observable groundwork started on the proof side: #2301 (pointer-based mstore blocks — the mstore(add(__evt_ptr, off), value) shape) and #2302 (execIRStmt_log: log0..log4 append exactly encodeYulLogEvent, nothing else changed). Next composition: scalarEventUnindexedStores blocks + topic evaluation → full scalar-event emission observable.

[Th0rgal]

Event-observable toolkit complete on the proof side (#2301-#2305): pointer/expression store blocks, memory-insensitivity of normalizeEventWord wrappers, the emitted-block shape pin, and the log-append observable. The scalar-event emission observable is now a direct composition; dynamic payloads (bytes/struct args, this issue's main scope) additionally need the dynamic-copy paths.