Align v1.0 documentation with current analog capture behavior and limits

[Copilot]

This updates the user-facing PicoMSO docs to match the current v1.0 analog scope behavior. It removes outdated single-channel/older-depth wording and makes the analog limits, mixed-mode behavior, and protocol descriptions consistent across the repo.

• README updates

  • Revised the oscilloscope summary to reflect v1.0 support for 1-channel and 2-channel analog capture
  • Updated analog capture depth to 40 ksamples per enabled analog channel
  • Documented resolution behavior:
    • 1 analog channel -> 12-bit
    • 2 analog channels -> 8-bit internal capture
  • Clarified that dual-channel analog is still delivered through the existing 16-bit scope stream format
  • Added a dual-analog sigrok-cli example

• Architecture docs

  • Added a concise v1.0 analog capability summary to docs/architecture.md
  • Clarified that mixed-mode keeps logic and scope as separate streams, while dual-analog interleaving happens only inside the scope stream

• Protocol docs

  • Updated docs/protocol.md to describe current 1-channel vs 2-channel analog behavior in user-facing terms
  • Clarified round-robin/interleaved dual-channel sampling and per-channel capture depth wording
  • Kept the protocol description conservative while noting that host integrations continue to consume the existing 16-bit scope stream format

• Developer-facing module docs

  • Updated firmware/mixed_signal/README.md so the mixed-signal backend summary matches the current documented v1.0 analog scope behavior

Example of the updated user-facing usage:

sigrok-cli -d picomso --channels A0,A1 --samples 1000 --config samplerate=5k