docs: update to align with current implementation

[robekl]

Summary

Documentation-only PR to align main docs with current dev behavior and protocol details.

High-Level Changes by Category

Companion Behavior & Routing

• Updated docs to reflect that companion nodes do not repeat by default.
• Added/clarified optional companion client repeat mode and its constraints.

CLI Documentation

• Added missing commands and corrected command details/defaults.
• Fixed outdated command descriptions and minor terminology issues.

Companion Protocol

• Updated protocol version references.
• Corrected frame formats, field sizes, packet meanings, and units.
• Added missing details for repeat-mode-related protocol fields.

Payload & Packet Specs

• Corrected payload field semantics and tag/ack descriptions.
• Replaced stale version-specific wording with current implementation behavior.
• Filled incomplete payload sections with implementation-aligned definitions.

FAQ Accuracy

• Updated answers that were out of date with current implementation.
• Corrected OTA/WiFi setup references and minor wording/grammar issues.

[liamcottle]

Other than the couple of comments I added, everything else looks pretty good thanks :)