Restate C-226's declared omission: nested field receiver paths now lower (almide#2933)

[O6lvl4]

C-226's statement ends with a declared omission:

DECLARED OMISSION: a nested receiver path (h.i.xs, xs[i].f) is still refused with the same list-push-nonvar — the field write takes one var and one field — and tests/list_push_on_record_field_test.rs pins that it stays a wall rather than silently widening.

almide/almide#2933 lowers every mut form through a record field path of any depth that is a chain of field reads ending in a var:

• list.push, list.pop and list.clear
• string.push and string.clear
• map.insert, map.delete and map.clear

The var may be a record var or a mut record parameter. The output is byte-identical to native, and every level is copy-on-write, so C-033 still holds. The new evidence is fixture spec/wasm_cross/nested_field_path_mut.almd (@contract: C-226, C-033).

A receiver that goes through an index or a call (xs[i].f, f().xs) is still refused.

Proposed restatement of the omission sentence:

A receiver path of any depth made of field reads from a var (h.i.xs) takes the same copy-on-write write at every level (#2933). DECLARED OMISSION: a receiver reached through an index or a call (xs[i].f) is still refused with list-push-nonvar / list-pop-nonvar.

The almide PR leaves the statement bytes unchanged, so the als-pin gate stays green. It carries the implementation and the fixture, and flags the stale sentence. The restatement then follows the als-first order: this ledger, then the pin advance, then the statement sync.