Migrate to espressif32 8.x (esp32 CI pinned to 7.1.3 meanwhile) #316

Background

espressif32 was the repo's only unpinned embedded platform and auto-drifted to 8.0.0 (released 2026-10-19 10:06 UTC — hours after the last green develop CI run at 00:22 UTC). Every PR opened since fails the Build (esp32) matrix job. The first hit was #315, whose diff cannot even affect the failing file (WifiControl.cpp compiles to an empty TU in matrix configs because WIFI_ENABLED is never set).

The immediate unblock is pinning espressif32@7.1.3 (last version CI ran green on, 2026-09-11). This issue tracks the actual 8.x migration so the pin can be lifted.

Known breakage on 8.0.0

src/Declination.cpp:49:

snprintf(achBufDeg + used, remaining, " (%s, %s)", valStr.c_str(), hoursStr.c_str());

error: ')' directive output may be truncated writing 1 byte into a region of size between 0 and 28 [-Werror=format-truncation=]

The 8.x GCC proves that writing the fixed tail of " (%s, %s)" into the remainder of the 32-byte global achBufDeg can truncate. The code has been unchanged since #281 (May 2026) and is green on 7.x, so this is purely the toolchain's stricter analysis — though the analysis is not wrong: worst-case runtime truncation is theoretically possible today (degree string ~9 chars + " (" + valStr + ", " + hoursStr + ")" can reach ~31 chars in a 32-byte buffer). A proper fix would assemble the tail into a fixed-size local and append with a bounded copy (or grow achBufDeg and restructure), rather than suppressing the warning.

Note: the CI run died at the first matrix configuration, so this is only the first known break — a full matrix run on 8.0.0 may surface more (including any arduino-esp32 core API changes bundled in the 8.0.0 major bump).

Work items

• Fix Declination.cpp truncation warning properly (bounded assembly, not -Wno-format-truncation)
• Run the full esp32 matrix on 8.0.0 and triage everything else it flags
• Review espressif32 8.0.0 release notes for Arduino core / toolchain changes affecting the firmware (WiFi API, FreeRTOS, etc.)
• Bump the pin in platformio.ini, then watch CI

Related drift risk

The RP2040 envs pin platform-raspberrypi by git URL without a commit hash (floats with that repo's default branch). Lower frequency than registry releases, but the same class of unpinned dependency.

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