v2 resolve/infer: payload-binder facts and untyped lambda arguments (re-derives N7)

[gunbai-bot]

Re-derives N7 on current main (not a rebase of #13558 / #13623, which are history only), plus rule A' and the empty-fold check.

What changed (src/v2/compiler)

• 03_resolve: a payload binder whose variant field is typed by the declaring type's formal is recorded as owed (LexicalBinderStanding: Declared / Valued / OwedFormal / Untyped); the resolve-time refusal resolve_reason_pattern_payload_formal_uninstantiated is gone.
• 04_infer: the owed binder is paid at arm entry from the scrutinee's instantiated arguments, read through transparent aliases (List<T> = FreeMonoid<T>), instantiating the field type itself.
• Three defects found on the chain, each fixed at its own boundary: the caller-admission wall judged a generic type instantiation as a call (callee_unreadable, also on main); match arms were compared without alias normalization; coproduct reading did not unfold the scrutinee alias.

Decisions (recorded in recurring_failure_mode/payload_binder_refused_at_resolve_instead_of_owed_to_infer)

• Untyped lambda argument: v2 types it only from its consumer (fold member/carrier frame, application formal), never from its own body; unconsumed stays not-derived. Type undeclared lambda actuals from preceding application formals (N7 token_stream) #13623's prefix typing is NOT carried (refuse, never widen). A correction of the seed rule.
• Rule A' (Type parameters bind only inside their own declaration (rule 2 / A'; stacks on #13260) #13265): v2 already refuses a leaked type parameter at resolve; pinned with the Result.ok-style sibling red. No code carried.
• Empty fold (fold_list empty: [] no longer locks the accumulator as List<Unit> #13475): v2 never types Empty/[], so no List lock; the carrier stays not-derived. Residual Cons { tail: acc } refusal is a declared red, next trigger: carrier typed from the fold's declared result.
• Derived-node identity step 2, shape 2: unify_generics reads a container slot through child_type_node #13330 read for the identity idea only; not ported (separately re-derived by another lane).

Receipts (claim_batch on a seed built from this head): infer_payload_binder_test 11/11, variant_field_infer_probe 13/13, parameter_reference 14/14, binder_admission pair 2+9, infer_fold_member_instance 6/6, caller_admission_native_wall 9/9. Instruments run in my container (srv1 ssh denied; no systemd-run there either, container cap is 24 GiB): gunbc test //gunbc/instruments:self-host exit 0, //gunbc/instruments:v2-native-cli exit 0.

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