feat: add ESP32-C3 MicroClaw port

[Jorel97]

Fixes #13.

/claim #13
Bounty board submission for the MicroClaw ESP32 Port ($350).

Covers #1, #2, #3, #4, and #5 with one integrated ESP32-C3 firmware port, while keeping a classic ESP32 PlatformIO environment buildable for the bounty's compatibility requirement.

Summary

• configure PlatformIO for ESP32-C3 DevKitM-1 and ESP32 Dev Module with MQTT, DHT22, battery, sleep, and OTA build flags
• add a configurable DHT22 driver with explicit failed-read handling and PicoClaw-compatible JSON output
• add retained MQTT status, sensor, warning, and critical alert topics under clawland/{node_id}/...
• add ADC battery monitoring, low-battery alerts, and configurable deep sleep wake cycles
• add ArduinoOTA maintenance window on every wake for field firmware updates
• add wiring guide for DHT22, DS18B20, PIR, relay, and battery sense pins
• add MQTT telemetry contract documentation and a dependency-free validation script for structure checks when ESP32 hardware is unavailable

Validation

• node scripts/validate-esp32-port.mjs
• node --check scripts/validate-esp32-port.mjs
• git diff --check
• platformio run -e esp32c3 succeeded
  • RAM: 43,404 bytes / 327,680 bytes (13.2%)
  • Flash: 800,670 bytes / 1,310,720 bytes (61.1%)
• platformio run -e esp32 succeeded
  • RAM: 49,200 bytes / 327,680 bytes (15.0%)
  • Flash: 809,045 bytes / 1,310,720 bytes (61.7%)

Hardware behavior is not claimed as hardware-tested until run on a physical board.

Bounty board reference: https://clawland.ai/pages/bounty

[Jorel97]

Maintenance verification after competitor activity on the bounty thread:

• node scripts/validate-esp32-port.mjs -> passed
• node --check scripts/validate-esp32-port.mjs -> passed
• platformio run -e esp32c3 -> passed
  • RAM: 43,404 bytes / 327,680 bytes (13.2%)
  • Flash: 799,486 bytes / 1,310,720 bytes (61.0%)
• git diff --check -> passed

I also updated the PR body from Refs #13 to Fixes #13 so the $350 bounty issue association is explicit.

[Jorel97]

Follow-up update to keep this aligned with the bounty text and easier to review:

• added a classic esp32 PlatformIO environment alongside esp32c3, so the existing ESP32 dev target remains buildable
• added retained lifecycle status telemetry on clawland/{node_id}/status
• documented the MQTT topic/payload contract in docs/telemetry-contract.md
• extended the local validator to require the ESP32 environment and telemetry contract

Validation rerun:

• node scripts/validate-esp32-port.mjs
• node --check scripts/validate-esp32-port.mjs
• git diff --check
• platformio run -e esp32c3 succeeded: RAM 43,404 / 327,680 bytes (13.2%), flash 800,670 / 1,310,720 bytes (61.1%)
• platformio run -e esp32 succeeded: RAM 49,200 / 327,680 bytes (15.0%), flash 809,045 / 1,310,720 bytes (61.7%)

Still not claiming physical hardware validation; this is compile- and structure-validated pending board testing.

[LuuOW]

Technical audit: code patterns and architectural layout verified for system reliability.