[bseverns]

Motivation

• Make each supported sensor easier to understand and teach by exposing expected signal shapes, normalization behavior, and common failure modes.
• Provide hands‑on wiring, RC recipes, calibration steps, and expected gesture behavior so newcomers can get a kit running quickly.
• Surface these practical notes in the main docs so instructor/repairer workflows are discoverable without digging through code.

Description

• Added inline explanatory comments to each firmware sensor implementation (makey_sensor.cpp, time_of_flight_sensor.cpp, piezo_sensor.cpp, pir_sensor.cpp, electret_mic_sensor.cpp, i2s_mic_sensor.cpp) describing expected signal ranges, normalization behavior, and common failure modes.
• Added per‑sensor field notes under docs/Sensors/ (MakeyTouch.md, TimeOfFlight.md, Piezo.md, PIR.md, ElectretMic.md, I2SMic.md) with wiring notes, recommended RC values, live calibration steps, and gesture expectations.
• Cross‑linked the new sensor pages from docs/SensingSurvey.md and the top‑level README.md to make the notes discoverable.
• Small editorial/formatting updates to docs to present the field notes as the go‑to hands‑on reference.

Testing

• No automated tests were executed; changes are inline comments and documentation only.
• The change was committed locally and is ready for CI (the repo CI still runs the standard firmware builds and pio test suite on pull request as configured).

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Codex Task