* Use consistent notation for array registers

Array registers should be clearly indicated in the table and hyperlinks.
The length of all array registers is now clearly indicated in the
register specification.

* Simplify register description and normalize casing
* Add length to all register specifications
* Avoid duplicating register length

* Add sender/receiver schematic
* Specify audio cable size
* Add link to pico hardware template
* Move physical connector PDF to assets
* Adopt requirement key words from RFC 2119
* Reorganize document sections for consistency and improve wording
* Add explicit transmission packet diagram
* Moved voltage requirement into main specification
* Replace oscilloscope picture with logic trace
* Clarify the sender MUST isolate the clock output
* Clarify how the receiver should adjust their clock

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Co-authored-by: Sonya Vasquez <[email protected]>

To further clarify and separate the specification of device operation
from the binary protocol, we move all messaging patterns to Device.md.

This greatly reduces the number of cross-references and duplicate
terminology across both documents.

* Remove ambiguous versioning string
* Move error handling to messaging patterns section
* Clarify rejection of register writes
* Account for possibility to flag events as errors

In the near-future we may want to use this as an explicit exception
throwing mechanism used by the Parse operator.

* Clarify error handling recommendations
* Improvements for register and serial interface
* Improve wording for describing connection checks
* Improve wording to clarify response contents

Specifically, we want to clarify the payload should send the register
contents after the request is processed.

* Fix broken header link

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Co-authored-by: bruno-f-cruz <[email protected]>