Console::Poll can terminate under heap pressure while growing bounded input line

[LK-Simon]

Bug

Console::Poll() enforces ConsoleConfig::MaximumLineLength, but the backing std::string grows incrementally with push_back(). Under severe heap pressure this growth can throw std::bad_alloc; if exception allocation itself fails on ESP32, the process reaches std::terminate()/abort().

This was reproduced in EventConsole-Lab after ESP-NOW had already begun reporting allocation failures. The fatal backtrace resolved through std::string::push_back() -> ESPressio::Serial::Console::Poll() -> operator new -> std::terminate().

Expected

A configured bounded console line should allocate its bounded storage during initialization rather than introducing an avoidable allocation point while consuming an ordinary command.

Acceptance criteria

• Reserve the configured line capacity during Console::Initialize().
• If the reservation cannot be satisfied, initialization fails cleanly rather than leaving a partially initialized console.
• Poll() does not need to grow the input string for lines up to MaximumLineLength.
• Add regression coverage demonstrating that the configured capacity is established during initialization and retained through polling/clearing.
• Preserve existing maximum-line-length/discard semantics and public API behavior.
• Update CHANGELOG/documentation for the patch release candidate.