dissolve: inline fold algebra scaffolding after #4736 generic instantiation

[briansrls]

Summary

Dissolves two 🟡 bootstrap-limitation marks whose dissolve-on (node://adhoc-f581ce40-042, landed via #4736) has fired. Inline named algebra step fns back into struct literals and delete the scaffolding (−28 net LOC).

• 03_name_resolve.dag: named_exports_topdown_{init,child_context,step} inlined into named_exports_topdown_algebra() NodeFoldTopDown literal.
• bounded_lattice_completeness.dag: infer_partial_bounded_lattice_instances_fold_{init,step} inlined into partial_bounded_lattice_instances_in_tree NodeFold literal. Dissolve-on condition (b) verified: List<Node> from [] / [n0] in anonymous init body type-checks inline. Step uses fold_list_right (substrate equivalent to builtin fold+list_snoc_item; builtin fold is not in scope inside nested struct-literal lambdas).

Mechanical refactor only — no behavior change.

Test plan

• cargo test -p v2-compiler-tests generic_instantiation — 5 passed (incl. v4_name_resolve_compiles_with_fold_list_dissolution, v4_nodefold_topdown_inline_algebra_compiles_and_runs)
• Local ci_floor_emit probe (v4-m1-rust-emit-probe.sh) — 474 files emitted, 0 diagnostics
• CI green on PR (incl. ci_floor_emit, v4_lens_gate, v4_lens_ci)