Bump to OCCT 8.0.1

Four mechanical binding edits; the bound Python surface is unchanged
(sigdiff compared the 7.9.3.1 dump against 8.0.1.1's in both directions
and found no class, member or constructor arity moved), so the app needs
no change.

- NCollection_Utf8String is gone; NCollection_String is the same UTF-8
  type. Python name kept, since the app imports it.
- Standard_Failure lost its Standard_Transient RTTI when it moved to
  deriving std::exception; ExceptionType() replaced DynamicType()->Name()
  and returns the same class names the exception dispatch keys on.
- FindKey gained a size_t overload beside the int one, so the plain
  member pointer is ambiguous; overload_cast picks the int form, which
  keeps the negative-index guard.
- StdPrs moved from TKService to TKV3d, so CMakeLists links both.

The byte-identity fixtures did NOT retire, contrary to the watchlist:
all six round-trip to the same digests under the new kernel, as do the
measurement, history and mesh-count blocks, so tests/data is untouched
and the app's content-addressed BREP payloads stay valid.

Gates: binding suite 83 passed, 138/138 symbols, sigdiff clean both
directions, ASAN clean, app suite 1798 passed / 1 skipped (unchanged),
sweep over 4486 parts with anchors_digest and every status unchanged,
-m perf 16% faster on the 32-feature chain.

docs/design.md

@@ -236,26 +236,48 @@ were gated:
   `IsDeleted` maps compared exactly, since that is the substrate the app's
   topological naming is built on.
 
-## OCCT 8.0 watchlist
+## OCCT 8.0 bump — what actually moved
 
-Recorded as each module landed, so the 10E bump is a known quantity:
+Done at 8.0.1 (2026-08-11). Four edits across ~4 000 lines of binding, and the
+bound Python surface came out **identical** — `sigdiff` compared 7.9.3.1's dump
+against 8.0.1.1's in both directions and found no class, member or constructor
+arity changed, so the drop-in contract held without the app being touched.
 
-- `Standard_Failure` derives `std::exception`, and the `Raise`/`Throw`/
-  `Instance` static helpers are gone. None of them is bound, so the exception
-  table should port unchanged.
-- `GeomLProp` is superseded by the new `GeomProp`/`BRepProp` packages, whose
-  results come back as structs with `IsDefined` flags instead of throwing. Only
-  `GeomLProp_SLProps.Normal` is bound, so this is a one-line move.
-- `StdPrs_BRepFont` and `StdPrs_BRepTextBuilder` become deprecated typedefs of
-  `Font_BRepFont`/`Font_BRepTextBuilder`. They are real classes in 7.9.3 and are
-  bound as such; 8.0 makes it a rename behind the same `OCP.StdPrs` names.
-- Methods that returned handles through an out-parameter return them by value.
-  `BRep_Tool.Surface`/`Curve` and the adaptors are the ones this binding
-  touches.
-- The global math wrappers are deprecated in favour of `std::`. Nothing here
-  binds them.
-- The byte-identity fixtures retire at the bump: a different kernel legitimately
-  writes different BREP bytes. The measurement and history blocks stay.
+What broke, all of it mechanical:
+
+- **`NCollection_Utf8String` is gone.** `NCollection_String`
+  (`NCollection_UtfString<char>`) is the same UTF-8 type and is what the font
+  API takes. The Python name is unchanged, since the app imports it.
+- **`Standard_Failure` lost its `Standard_Transient` RTTI** when it moved to
+  deriving `std::exception`, so `DynamicType()->Name()` no longer compiles. The
+  virtual `ExceptionType()` replaced it and returns the same class names, which
+  is what the exception dispatch keys on — and what `cad_pool` marshals home.
+- **The `Size()` → `size_t` migration added index overloads.** `FindKey` on the
+  indexed maps now has both an `int` and a `size_t` form, so a plain member
+  pointer is ambiguous; `nb::overload_cast<Standard_Integer>` picks the `int`
+  one, which keeps the negative-index guard.
+- **`StdPrs` moved from TKService to TKV3d**, so `CMakeLists.txt` links both.
+
+Three watchlist predictions were wrong, recorded here because the reasoning
+behind them was plausible:
+
+- `StdPrs_BRepFont`/`StdPrs_BRepTextBuilder` did **not** become typedefs of
+  `Font_BRepFont`/`Font_BRepTextBuilder`. The aliasing runs the other way — they
+  are still the real classes and the `Font_*` names are the typedefs.
+- `GeomLProp` was **not** superseded by `GeomProp`/`BRepProp`. It became a
+  template (`GeomLProp_SLProps` is now an alias for
+  `GeomLProp_SLPropsBase<handle<Geom_Surface>>`) and kept the constructor and
+  accessors this binding uses, so the module compiled unchanged.
+- **The byte-identity fixtures did not retire.** A different kernel was assumed
+  to write different BREP bytes; 8.0.1 does not. All six fixtures round-trip to
+  the same digests, and the measurement, history and mesh-count blocks match
+  too, so `tests/data/` was left alone and no re-bless happened. That also means
+  the app's content-addressed BREP payloads stay valid across the bump.
+
+Unchanged as predicted: the handle model (`occt_handle.h` needed nothing, ASAN
+clean), the exception *table* (the removed `Raise`/`Throw`/`Instance` helpers
+were never bound), the deprecated out-parameter handle returns this binding
+still uses, and the global math wrappers it never bound.
 
 ## Open questions