feat(skills): add IoT edge skills and align agent/instruction docs (#1431)

* feat(skills): add IoT edge skills and align agent/instruction docs

* fix(ci): handle fork permission errors in plugin structure check

* fix(ci): allow intentional Spanish vocabulary in codespell

* docs(skills): translate IoT edge skill content to English

* fix(ci): pass codespell and README validation

* chore: regenerate skills index after merge

skills/arduino-azure-iot-edge-integration/references/arduino-iot-checklist.md

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+# Arduino Azure IoT Checklist
+
+Use this checklist before finalizing architecture or implementation guidance.
+
+## 0) Official Arduino Baseline
+
+- Official references reviewed from <https://www.arduino.cc/en/Guide> and <https://docs.arduino.cc/>.
+- Language/API calls validated against <https://docs.arduino.cc/language-reference/>.
+- Best practices reviewed from `references/arduino-official-best-practices.md`.
+
+## 1) Device Profile
+
+- MCU model and memory constraints documented.
+- Sensor list and sampling strategy defined.
+- Power model documented (mains, battery, sleep cycles).
+
+## 2) Connectivity
+
+- Selected transport documented (MQTT over TLS preferred).
+- Network failure behavior defined.
+- Local timestamp strategy defined if device lacks RTC sync.
+
+## 3) Security
+
+- Unique identity per device.
+- No secrets in source control.
+- Credential rotation plan documented.
+- Firmware update and rollback plan documented.
+
+## 4) Edge and Cloud Flow
+
+- Routing from edge to IoT Hub documented.
+- Offline buffering limits defined.
+- Duplicate handling strategy documented.
+- Alerting thresholds and destinations defined.
+
+## 5) Validation
+
+- Connectivity soak test scenario.
+- Packet loss and reconnection test.
+- Command authorization test.
+- Firmware version and health reporting verification.

skills/arduino-azure-iot-edge-integration/references/arduino-official-best-practices.md

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+# Arduino Official References and Best Practices
+
+Use these official Arduino resources before finalizing firmware or hardware guidance.
+
+## Official References
+
+- Arduino main guide: <https://www.arduino.cc/en/Guide>
+- Arduino docs home: <https://docs.arduino.cc/>
+- Getting started path: <https://docs.arduino.cc/learn/starting-guide/getting-started-arduino/>
+- Arduino IDE usage: <https://docs.arduino.cc/learn/starting-guide/the-arduino-software-ide/>
+- Arduino language reference: <https://docs.arduino.cc/language-reference/>
+- Arduino programming reference overview: <https://docs.arduino.cc/learn/programming/reference/>
+- Arduino memory guide: <https://docs.arduino.cc/learn/programming/memory-guide/>
+- Arduino debugging fundamentals: <https://docs.arduino.cc/learn/microcontrollers/debugging/>
+- Arduino low-power design guide: <https://docs.arduino.cc/learn/electronics/low-power/>
+- Arduino communication protocols index: <https://docs.arduino.cc/learn/communication/>
+- Arduino style guide for libraries: <https://docs.arduino.cc/learn/contributions/arduino-library-style-guide/>
+
+## Firmware Best Practices
+
+- Keep the `loop()` non-blocking; avoid long `delay()` usage in production logic.
+- Use `millis()`-based scheduling for periodic tasks.
+- Budget SRAM explicitly and avoid dynamic allocation in hot paths.
+- Validate sensor ranges and provide safe defaults for invalid readings.
+- Add startup self-checks and periodic health heartbeat messages.
+- Version the payload schema and firmware version in every telemetry stream.
+- Implement retry with exponential backoff and jitter for network operations.
+- Store credentials outside source code and rotate them according to policy.
+
+## Hardware and Power Best Practices
+
+- Document voltage levels, pin mapping, and current limits per peripheral.
+- Design for brownout and power fluctuation scenarios.
+- Use watchdog and safe recovery behavior where available.
+- Plan low-power modes for battery deployments and validate wake cycles.
+
+## Integration Best Practices for Azure IoT
+
+- Prefer secure transports (MQTT over TLS) and per-device identity.
+- Define idempotent upstream processing for duplicate message scenarios.
+- Include device health metrics (uptime, reset reason, RSSI where applicable).
+- Validate offline buffering bounds to avoid uncontrolled memory growth.