Six electronics experiments

Complete exact accepted source readers, blank worksheets and original diagrams. Physical and target qualification remain separate.

1. 93 — TPS22919: Switching a Sensor OFF Does Not Remove Every Power Path
2. 94 — Pico Leak Probe: Reverse the Excitation, Then Measure the Imbalance
3. 95 — Soil Dry-Back: Estimate a Rate Without Averaging Across a Refill
4. 96 — SPS30: Fan Cleaning Is Not a Fresh Particle Measurement
5. 97 — Multiroom MQTT: A Retained Message Can Outlive Its Sensor
6. 98 — Pico PIO Capture: A Full FIFO Changes the Experiment