[bdbarnett]

Three text fixes to the esptool steps on the firmware page.

• The write-flash step now says a faster USB-serial bridge can take --baud 921600; the plain line still works.
• The app-only update line under the files table now carries --port COM3, like the main steps.
• The install step now creates and activates a virtual environment (Windows and Linux/macOS), so the esptool that runs is the one just installed.

Targets the firmware-page-staged branch, which is not served. Rendered locally: all three appear for the ESP32-P4 board, no console errors.