docs: write the v0.11.1, v0.12.0 and v0.12.1 changelog entries

CHANGELOG.md

@@ -21,10 +21,58 @@ minor versions, as the README states. Releases before v0.2.0 predate this file.
 
 ## v0.12.1 — 2026-09-24
 
+### Fixed
+
+- A boolean clip whose second operand is an `IfcPolygonalBoundedHalfSpace` or
+  `IfcBoxedHalfSpace` is now applied instead of the element degrading to a
+  bounding box. The gate tested `IsA("IfcHalfSpaceSolid")`, and
+  `step.Instance.IsA` matches the exact type keyword only — so the subtypes
+  never passed, and the bounded-clipping path below the gate was unreachable.
+  That is Revit's standard mitred wall/slab/beam join. On the public corpus the
+  box-fallback rate goes from 1.9% to **0.0%** on `duplex_a` and from 2.4% to
+  **0.0%** on `fzk_haus`, and `UnhandledItemTypes` no longer reports
+  `IFCPOLYGONALBOUNDEDHALFSPACE`. The freed elements land as extrusions, since
+  a clipped mesh keeps the source of its first operand.
+
+  The bounded clip only applies when the boundary polygon is its own
+  axis-aligned bounding box — a rectangle, which is what Revit exports. For any
+  other shape, clipping against the AABB would remove more material than the
+  real boolean does and under-report the element, so the clip declines and the
+  element keeps the conservative box. The rectangle test compares the polygon's
+  shoelace area with its AABB's area at a relative tolerance of 1e-12, computed
+  relative to the first vertex: on a site-placed millimetre model the raw sum
+  cancels coordinates near 1e6 and would misjudge the area.
+
 ## v0.12.0 — 2026-09-24
 
+### Added
+
+- `IfcFaceBasedSurfaceModel` is tessellated. It had no dispatch case, so every
+  element built from one degraded to a bounding box; it was the largest entry in
+  the measured gap list. `duplex_a` goes from a **32.1%** box-fallback rate to
+  **1.9%** — 65 elements move from box to brep, and nothing else moves. The
+  surface model shares its traversal with `IfcShellBasedSurfaceModel`: both are
+  a set of face sets that `brepMesh` already tessellates.
+
 ## v0.11.1 — 2026-09-24
 
+### Fixed
+
+- A self-referencing or cyclic `IfcLocalPlacement.PlacementRelTo` chain no
+  longer kills the process. Placement composition recursed with no cycle check
+  and no depth bound, so `#12=IFCLOCALPLACEMENT(,#12);` overflowed the stack —
+  a `fatal error`, not a panic, so `recover()` could not catch it. It was
+  reachable from `goifc.Assemble` on arbitrary input, and every release through
+  v0.11.0 is affected: upgrade if you import files you did not author.
+
+  The chain walk now detects cycles and is capped at 1024 levels. Both are
+  needed: IFC bounds placement depth nowhere, so a cap alone would have to be
+  tight enough to truncate legal chains, and detection alone would still let a
+  crafted acyclic chain of a million placements exhaust the stack. A cyclic or
+  over-deep chain resolves to the identity for the part it cannot compose — the
+  same answer a missing placement gives. Real buildings nest two to four deep,
+  and at that depth the walk allocates nothing.
+
 ## v0.11.0 — 2026-09-23
 
 ### Added