[robdobsn]

Summary

The serial monitor now chooses the baud rate itself, and checks it, when -b isn't given. This applies to raft monitor and to the monitor at the end of raft run.

• Which ports: only a real UART, meaning a USB-UART adapter or a non-USB port. The ESP32's native USB (vendor ID 303a) ignores the rate and isn't checked.
• -b given: that rate is used and never changed.
• Starting rate, the first that's known:
  1. the built firmware's console rate (CONFIG_ESP_CONSOLE_UART_BAUDRATE in build/<SysType>/raft/sdkconfig, when the console is on a UART)
  2. the rate last found working on this adapter
  3. the -b from last time (raft.info)
  4. 115200
• Checking: if the output is unreadable for more than 0.5 s, other rates are tried until log text is readable. Each change is shown in the output and in the log file. Without -b, a rate saved in raft.info is now only a starting point and no longer fixes the rate.
  • "Unreadable" means under 70% text bytes, or 6 or fewer distinct byte values with less than 90% text, and no log lines.
  • The boot ROM's output (always at 115200) is never taken as a sign the rate is right or wrong.
  • Once text has been read, 3 s of unreadable output is needed before trying again, so a burst of binary data doesn't change the rate.
  • If no rate gives readable text, the most readable one is kept and the search repeats after 10 s.
• Remembering: the rate found is saved per adapter (USB IDs and serial number, or the port name) in monitor_bauds.json in the user's config folder (~/.config/raft, or %APPDATA%\raft on Windows).
• WSL: -b is passed to raft.exe only when given. Otherwise raft.exe chooses the rate, because only it can identify the adapter.

README: new Monitor baud rate section. The -b help text was updated for monitor and run.

Testing

• cargo test: 162 passed, 15 of them new. A simulated UART receiving at the wrong rate covers 12 rate pairs, plus the detector, a reset during boot, a binary burst, the starting-rate order, sdkconfig parsing and the adapter store.
• On hardware: an Axiom (ESP32-S3) with a CH340 adapter on UART0 (COM17), Windows raft.exe built from this branch, and resets through the Axiom's USB port.
  • With firmware at 115200:
    • nothing known: 115200, readable
    • 921600 wrongly remembered: switched to 115200 after about 1 s
    • -b 921600: stayed at 921600, unreadable as expected
    • native USB port: not checked
  • With firmware at 921600:
    • from the project folder: started at 921600 from the build's console setting
    • 115200 remembered, or nothing known: switched to 921600 0.5 s after the unreadable output began
    • three resets while at 921600: no switch
    • WSL hand-off to raft.exe: started at 921600 from the build's console setting

This PR and #15 both change the run handler in main.rs, so whichever merges second needs a small conflict fixed.

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