feat(tests): populate test_categories.toml with cross-cutting entries

tests/test_categories.toml

@@ -0,0 +1,28 @@
+# Hand-curated registry for cross-cutting and ambiguous tests.
+# Auto-inferred records that are correct do NOT need entries here.
+# Generated 2026-06-08 from --audit --strict output.
+# Strict mode found zero cross-cutting auto-classified files (no file has
+# multiple subsystems in auto-inference). Registry exists for future
+# cross-cutting entries the user may identify.
+
+[files.test_arch_boundary_phase1]
+subsystems = ["architecture", "mma"]
+batch_group = "mma"
+notes = "Phase 1 of arch-boundary refactor; explicit cross-cutting label"
+
+[files.test_arch_boundary_phase2]
+subsystems = ["architecture", "mma"]
+batch_group = "mma"
+
+[files.test_arch_boundary_phase3]
+subsystems = ["architecture", "mma"]
+batch_group = "mma"
+
+[files.test_tier4_interceptor]
+subsystems = ["tier4", "mma"]
+batch_group = "mma"
+notes = "Tier 4 QA interceptor; touches mma orchestration"
+
+[files.test_tier4_patch_generation]
+subsystems = ["tier4", "mma"]
+batch_group = "mma"