v0.1.0: Layout primitives + composable API — 23 new tests

Layout primitives (org/layout-primitives.org, ~290 lines):
- CLOS layout-node class wrapping YGNodeRef with tg:finalize for GC cleanup
- 12 setter functions with keyword→integer enum translation
- layout-calculate: runs Yoga layout, returns root
- 14 tests: dimension, direction, flex-grow, align, justify,
  padding, margin, absolute position, wrap, gap, nested layout

Composable API (org/layout-composable.org, ~200 lines):
- vbox/hbox macros: declarative container creation with style props
- overlay macro: absolute-positioned child over relative base
- spacer function: flex-grow filler
- make-props-list helper: extracts plist minus :children
- 6 tests: vbox stacking, hbox layout, spacer flex, overlay position,
  align/justify via vbox, padding offset

GREEN: 29/29 pass (59 assertions)
- yoga-ffi: 9 tests (22 assertions)
- layout-primitives: 14 tests (24 assertions)
- layout-composable: 6 tests (13 assertions)

docs/ROADMAP.org

@@ -37,11 +37,14 @@ every component after v0.1.0 uses the layout engine for positioning.
 - Bind core functions: ~node-new~, ~node-free~, ~node-style-set-*~, ~node-layout-get-*~, ~calculate-layout~
 - ~100 lines CFFI
 
-*** TODO Layout primitives
+*** DONE Layout primitives
 :PROPERTIES:
 :ID:       id-v010-layout-primitives
 :CREATED:  [2026-05-10 Sat]
 :END:
+:LOGBOOK:
+- State "DONE"  from "TODO"  [2026-05-11 Mon]
+:END:
 
 - ~(make-layout-node)~ — wraps a ~YGNodeRef~ in a CLOS object
 - ~(layout-node-set-dimension node width height)~ — sets width/height in points
@@ -59,11 +62,14 @@ every component after v0.1.0 uses the layout engine for positioning.
 - ~(layout-calculate root width height)~ — runs Yoga's calculateLayout, populates each node's computed x/y/w/h
 - ~200 lines CL
 
-*** TODO Layout composable API
+*** DONE Layout composable API
 :PROPERTIES:
 :ID:       id-v010-layout-composable
 :CREATED:  [2026-05-10 Sat]
 :END:
+:LOGBOOK:
+- State "DONE"  from "TODO"  [2026-05-11 Mon]
+:END:
 
 Convenience macros to build layout trees from CL function calls: