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/bmb/skills/bmad-agent-builder/assets/save-memory.md

@@ -0,0 +1,29 @@
+---
+name: save-memory
+description: Explicitly save current session context to memory
+menu-code: SM
+---
+
+# Save Memory
+
+Immediately persist the current session context to memory.
+
+## Process
+
+1. **Read current index.md** — Load existing context
+
+2. **Update with current session:**
+   - What we're working on
+   - Current state/progress
+   - Any new preferences or patterns discovered
+   - Next steps to continue
+
+3. **Write updated index.md** — Replace content with condensed, current version
+
+4. **Checkpoint other files if needed:**
+   - `patterns.md` — Add new patterns discovered
+   - `chronology.md` — Add session summary if significant
+
+## Output
+
+Confirm save with brief summary: "Memory saved. {brief-summary-of-what-was-updated}"