feat(v4.4): complete remaining v4.1-v4.4 features + precision tolerance + Euler ops

v4.1 收尾:
- IncrementalUpdateEngine: dirty flag propagation, cache invalidation
- LargeAssembly: InstanceCache, assembly instancing
- STEP import: robust/graceful parsing with skip tracking

v4.3 分析工具:
- Mass properties (volume, centroid, inertia tensor)
- Clearance analysis, wall thickness analysis
- Enhanced drawing: hidden-line removal, offset sections, BOM
- DXF import (LINE/CIRCLE/ARC/LWPOLYLINE/SPLINE → B-Rep extrusion)

v4.4 地基加固:
- ToleranceChain: RSS cumulative tolerance propagation (7 tests)
- Euler operations: MEV/KEV/MEF/KEF/KEMR/MEKR (20 tests)
- Replace hardcoded tolerances with ToleranceConfig in validate
- Fix incremental_update test API mismatch (15/15 pass on Linux)

Docs:
- v4.1-v4.4 development plans + roadmap updated
- v4.4 marked complete on Linux

30 files, +3424/-210

tests/brep/test_tolerance.cpp

@@ -91,3 +91,68 @@ TEST(ToleranceTest, ToleranceConfig_AllDefaultPositive) {
     EXPECT_GT(cfg.boolean, 0);
     EXPECT_GT(cfg.angular, 0);
 }
+
+// ── ToleranceChain tests ──
+
+TEST(ToleranceChainTest, EmptyChain) {
+    ToleranceChain chain;
+    EXPECT_EQ(chain.depth(), 0u);
+    EXPECT_EQ(chain.cumulative(), 0.0);
+    EXPECT_EQ(chain.max_step(), 0.0);
+}
+
+TEST(ToleranceChainTest, SingleStep) {
+    ToleranceChain chain;
+    chain.push("intersect", 1e-6);
+    EXPECT_EQ(chain.depth(), 1u);
+    EXPECT_DOUBLE_EQ(chain.cumulative(), 1e-6);
+    EXPECT_DOUBLE_EQ(chain.max_step(), 1e-6);
+}
+
+TEST(ToleranceChainTest, MultiStepRSS) {
+    ToleranceChain chain;
+    chain.push("a", 3e-6);
+    chain.push("b", 4e-6);
+    // RSS: sqrt(3² + 4²) * 1e-6 = 5e-6
+    EXPECT_DOUBLE_EQ(chain.cumulative(), 5e-6);
+}
+
+TEST(ToleranceChainTest, MaxStep) {
+    ToleranceChain chain;
+    chain.push("small", 1e-8);
+    chain.push("large", 1e-4);
+    chain.push("med", 1e-6);
+    EXPECT_DOUBLE_EQ(chain.max_step(), 1e-4);
+}
+
+TEST(ToleranceChainTest, ClearResets) {
+    ToleranceChain chain;
+    chain.push("x", 1e-6);
+    chain.clear();
+    EXPECT_EQ(chain.depth(), 0u);
+    EXPECT_EQ(chain.cumulative(), 0.0);
+}
+
+TEST(ToleranceChainTest, StepsAccess) {
+    ToleranceChain chain;
+    chain.push("op1", 1e-9);
+    chain.push("op2", 2e-9);
+    auto& steps = chain.steps();
+    ASSERT_EQ(steps.size(), 2u);
+    EXPECT_EQ(steps[0].first, "op1");
+    EXPECT_DOUBLE_EQ(steps[0].second, 1e-9);
+    EXPECT_EQ(steps[1].first, "op2");
+    EXPECT_DOUBLE_EQ(steps[1].second, 2e-9);
+}
+
+TEST(ToleranceChainTest, BooleanChainSimulation) {
+    ToleranceChain chain;
+    chain.push("intersect", 1e-6);
+    chain.push("split", 1e-6);
+    chain.push("classify", 1e-7);
+    chain.push("sew", 1e-5);
+    // Cumulative should be dominated by the sewer step
+    double cum = chain.cumulative();
+    EXPECT_GT(cum, 1e-5);
+    EXPECT_LT(cum, 1.5e-5);
+}