fix(v1.0.1): 修复 VDE-018 — ssi_boolean.cpp 命名空间回归

1. 删除不存在的 using vde::core::Transform3D/Plane3D
2. 移除两个过早关闭 vde::brep 命名空间的 } (原行431/946)
3. 移除匿名空间内重复的 extract_face_fragment/classify_point_adaptive 前向声明

GCC 10.2.1 -fsyntax-only 通过 (0 errors)

docs/feedback/VDE-018.md

@@ -0,0 +1,69 @@
+# VDE-018: ssi_boolean.cpp regression — face_bounds ambiguity, mesh/curves lookup, enum values
+
+- **ID**: VDE-018
+- **Date**: 2026-07-28
+- **Status**: Fixed
+- **Severity**: Critical
+- **Category**: COMPILE / GCC Compatibility
+- **Source**: ViewDesign fea/viewdesign-engine branch
+
+## Issue
+
+The merge of VDE-016 fix (2f69f06) and the subsequent main branch update (ff4c8d3) 
+introduced a regression in `ssi_boolean.cpp` that breaks GCC builds. The VDE-016 fix 
+moved `ClassResult` enum from the anonymous namespace to `vde::brep::ssi_boolean.h`, 
+but the enum values (`IN`, `ON`, `OUT`) are used unqualified throughout `ssi_boolean.cpp`.
+
+The subsequent attempt at fix (d5c00a0, July 28) only reordered `#include <iterator>` 
+and did not address the root causes.
+
+## Build Errors (GCC/MSVC with /permissive-)
+
+```
+error: 'OUT' was not declared in this scope; did you mean 'vde::brep::OUT'?
+error: 'IN' was not declared in this scope; did you mean 'vde::brep::IN'?  
+error: 'ON' was not declared in this scope; did you mean 'vde::brep::ON'?
+error: call of overloaded 'face_bounds(const vde::brep::BrepModel&, int)' is ambiguous
+  - candidate 1: anonymous ns definition (line 434)
+  - candidate 2: vde::brep forward declaration (line 42)
+error: 'get_mesh' was not declared in this scope
+error: 'core' has not been declared (in 'core::exact_orient3d')
+error: 'SSIBooleanResult' does not name a type
+error: 'curves' is not a class, namespace, or enumeration
+error: expected declaration before '}' token
+```
+
+## Root Causes
+
+1. **ClassResult enum moved to header** (`ssi_boolean.h:51`) but values (IN/ON/OUT) used unqualified in anonymous namespace
+2. **face_bounds/face_normal forward-declared in vde::brep namespace** (line 42-43) but defined in anonymous namespace — GCC sees both as candidates
+3. **get_mesh** defined as static in anonymous namespace but called from functions outside it (e.g., `classify_face_fragment`)
+4. **core::exact_orient3d** requires vde::core namespace qualification in GCC two-phase lookup
+5. **SSIBooleanResult** only forward-declared in header, not visible in anonymous namespace
+6. **curves::intersect_surfaces** lookup fails when `using namespace vde` not in scope
+
+## Suggested Fix
+
+**Root cause**: The merge of VDE-016 moved ClassResult from anonymous namespace to the public header, but `ssi_boolean.cpp` on main had three separate issues:
+
+1. `using vde::core::Transform3D;` and `using vde::core::Plane3D;` — these types don't exist in vde::core
+2. Two premature `}  // anonymous namespace` closures at lines 431 and 946 that closed `vde::brep` namespace early, pushing all subsequent functions (face_bounds, face_normal, classify_face_fragment, etc.) to global scope where BrepModel was not visible
+3. Duplicate forward declarations of `extract_face_fragment` and `classify_point_adaptive` inside the anonymous namespace that created ambiguity with the actual definitions in `vde::brep`
+
+**Fix applied (v1.0.1)**:
+1. Removed invalid `using vde::core::Transform3D;` and `using vde::core::Plane3D;`
+2. Removed the two premature `}` closures, keeping all code within `namespace vde::brep { ... }`
+3. Removed unused forward declarations from anonymous namespace
+
+GCC 10.2.1 `-fsyntax-only` passes cleanly (0 errors).
+
+## Known-Good Version
+
+`ssi_boolean.cpp` at commit `05b62e8` (feat(v5-M1): TrimmedSurface integration + SSI boolean) 
+builds cleanly on GCC with a minor compat header addition (`namespace mesh = vde::mesh`).
+
+## Current ViewDesign Workaround
+
+Reverted `ssi_boolean.cpp` to 05b62e8. Only this one file is reverted; the other 48+ 
+vde_brep .cpp files use latest API. This allows the rest of VDE to be integrated while 
+waiting for a proper fix.