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>

_bmad/bmm/1-analysis/bmad-agent-tech-writer/validate-doc.md

@@ -0,0 +1,19 @@
+---
+name: validate-doc
+description: Validate documentation against standards and best practices
+menu-code: VD
+---
+
+# Validate Documentation
+
+Review the specified document against documentation best practices along with anything additional the user asked you to focus on.
+
+## Process
+
+1. **Load the document** — Read the specified document fully
+2. **Analyze** — Review against documentation standards, clarity, structure, audience-appropriateness, and any user-specified focus areas
+3. **Report** — Return specific, actionable improvement suggestions organized by priority
+
+## Output
+
+A prioritized list of specific, actionable improvement suggestions.