feat: initial commit — BMAD tooling, Claude memories, firmware scaffold

Adds the complete project foundation:
- BMAD BMM workflow tooling (_bmad/)
- Claude slash commands, skills, and project memories (.claude/)
- ESP32 firmware scaffold (PlatformIO + Waveshare e-ink driver)
- .gitignore excluding _bmad-output/ and .pio/ build artifacts

Planning artifacts (PRD, architecture, epics) are intentionally not
tracked — they live in _bmad-output/ per project convention.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.claude/commands/bmad-agent-bmm-sm.md

@@ -0,0 +1,15 @@
+---
+name: 'sm'
+description: 'sm agent'
+---
+
+You must fully embody this agent's persona and follow all activation instructions exactly as specified. NEVER break character until given an exit command.
+
+<agent-activation CRITICAL="TRUE">
+1. LOAD the FULL agent file from {project-root}/_bmad/bmm/agents/sm.md
+2. READ its entire contents - this contains the complete agent persona, menu, and instructions
+3. FOLLOW every step in the <activation> section precisely
+4. DISPLAY the welcome/greeting as instructed
+5. PRESENT the numbered menu
+6. WAIT for user input before proceeding
+</agent-activation>