chore: upgrade BMAD framework to skill-based architecture

Migrates from slash-command files (.claude/commands, .cursor/commands)
to the new skill-based architecture with workflow step files.

_bmad/tea/workflows/testarch/bmad-testarch-trace/workflow-plan.md

@@ -0,0 +1,21 @@
+    # Workflow Plan: testarch-trace
+
+    ## Create Mode (steps-c)
+    - step-01-load-context.md
+
+- step-02-discover-tests.md
+- step-03-map-criteria.md
+- step-04-analyze-gaps.md
+- step-05-gate-decision.md
+
+  ## Validate Mode (steps-v)
+  - step-01-validate.md
+
+  ## Edit Mode (steps-e)
+  - step-01-assess.md
+  - step-02-apply-edit.md
+
+  ## Outputs
+  - {test_artifacts}/traceability-matrix.md
+
+- Gate decision summary (if evidence available)