04 — Tree and Node Contract After Commit

The tree is now hierarchical (live)

v_registries_pivot_node_contract.has_children flipped from 0 → 6 parents, with no view or UI change — the data-driven, no-hardcode-depth contract working exactly as designed.

parent node	has_children	child_pivot_codes	child_layer_kind
PIV-001 (Danh mục Total, 169)	true	{PIV-101, PIV-102, PIV-106}	cross-table
PIV-007 (DOT Tools Total, 309)	true	{PIV-104}	cross-table
PIV-009 (Collections Total, 168)	true	{PIV-105}	cross-table
PIV-016 (Loài Total, 42)	true	{PIV-103}	cross-table
PIV-101 (Danh mục theo Lớp)	true	{PIV-201, PIV-202, PIV-203, PIV-204, PIV-205, PIV-206}	l2-drill
MTX-L1-OVERVIEW (Ma trận L1, 1,131,998)	true	{MTX-L2-ATOM}	matrix

Parent vs leaf rendering (verified live)

node	is_root	has_children	count_value	final_substrate_ref
PIV-001	true	true	169	NULL (parent — no leaf substrate)
PIV-007	true	true	309	NULL
PIV-015	true	false	107	trigger_registry (leaf terminus)
PIV-019	true	false	1,131,998	birth_registry (leaf terminus)
PIV-104	false	false	NULL (group pivot)	dot_tools
PIV-201	false	false	NULL (group pivot)	meta_catalog

The contract correctly distinguishes:

• parents → has_children=true, final_substrate_ref=NULL, child_layer_kind set, child_pivot_codes[] populated;
• leaf totals → has_children=false, final_substrate_ref=<source table> (the L3/L4 "DB về chính nó" terminus);
• group pivots (PIV-101..106, 201..206, 103/104/105) → count_value=NULL + count_status=PIVOT_MISSING for the aggregate row (their counts live in child group rows — honest, not an error).

Layer examples (live)

• L1 (top totals): PIV-019 birth_registry 1,131,998; PIV-007 DOT 309; PIV-207 approvals 211; PIV-001 catalog 169; PIV-009 collections 168; PIV-016 species 42; etc.
• L2 (DOT drill, PIV-104 under PIV-007): category pivot=8, null=4, Vòng đời thực thể=2, Giám sát hệ thống=2 → Σ=16. (⚠ published-only filter; Σ16 ≠ parent 309 — see doc 06 drift flag.)
• L3 (substrate terminus): final_substrate_ref resolves each leaf to its source table (e.g. PIV-015 → trigger_registry, PIV-019 → birth_registry).

No naming-convention dependency

Hierarchy is resolved from parent_code (data edges), not from registry_group strings. §13 satisfied.