Shape List hierarchy phase 1: organizational groups and outliner

[trailcode]

Summary

Documents the Shape List organizational hierarchy and related import/outliner work landed in PR #216 (phase 1). Groups are folder nodes in the document tree (no parent transform inheritance). Follow-ups: #215 (phase 2), #214 (phase 3), #59 (broader assembly modeling).

Problem

• Shape List was a flat list of solids with no parent/child outliner.
• Multi-body STEP assemblies flattened; no way to organize parts into folders for visibility, selection, or parenting new geometry.
• Hide-all and selection UX did not support group-oriented workflows.

Implemented scope

Document model

• Shp nodes gain parent_id, sibling_order, is_group (empty compound; never displayed).
• .ezy persists parentId, order, isGroup, visible.
• Undo: Shape_tree_delta for reparent / group / ungroup; shape add/remove records include hierarchy fields.

Shape List UI

• Tree table: expand/collapse, vis / solid-wire / material on the left, name on the right.
• Current group: click a group (including empty) to set it; new primitives, extrudes, revolves, PLY, and unioned STEP import parent under it.
• New group / Group / Ungroup (all direct children move up); cascade delete of group subtrees.
• Drag-drop reparent (onto group, onto solid → that solid's parent, empty pad below list → document root).
• Ctrl multi-select; group click selects descendant solids.
• Persist ui.shapeList.expanded and ui.shapeList.currentGroupId.

Operations / import

• Booleans / polar dup: result parent = shared operand parent, else root.
• Hide all no longer stomps per-shape visibility flags (effective visibility via ancestors + overlays).
• STEP XCAF assembly → Shape List group tree (unless Union shapes); product/part names used when present.
• File → Import dialog (metadata, optional union) — related import UX on the same branch.

Tests / docs

• tests/shp_tests.cpp: group/ungroup, hierarchy JSON, fuse parent, current-group parenting, etc.
• docs/usage.md, CHANGELOG.md, src/doc/shape.md, gui.md, utility.md.

Acceptance criteria

• Group / ungroup / reparent / cascade delete with undo
• Current group; empty groups selectable; new solids parent under it
• DnD to group, to sibling-via-solid, and to document root (empty pad)
• Group visibility hides subtree; Hide all preserves per-node flags
• Boolean results inherit shared parent when applicable
• STEP assembly import as group tree (optional union)
• .ezy round-trip of hierarchy + UI expand/current group
• Unit tests and user/developer docs updated

Out of scope (follow-ups)

• Shape List hierarchy phase 2: reorder, duplicate group, selection polish #215 — sibling reorder without reparent, duplicate group, selection polish
• Shape List hierarchy phase 3: parent transforms and advanced assembly model #214 — parent transform inheritance, boolean history tree, part-local frames
• Compound / assembly modeling in EzyCad #59 — broader compound / assembly modeling

Related

• PR: Shape List hierarchy phase 1: organizational groups and outliner #216
• Shape List hierarchy phase 2: reorder, duplicate group, selection polish #215 Shape List hierarchy phase 2
• Shape List hierarchy phase 3: parent transforms and advanced assembly model #214 Shape List hierarchy phase 3
• Compound / assembly modeling in EzyCad #59 Compound / assembly modeling in EzyCad