Follow-up to PR #2073 (cc @jensenpat).

MeterModel.h:167 declares:

int m_activeTxSlice{0};

But MeterModel::clear() (MeterModel.cpp) resets it to -1:

m_activeTxSlice = -1;

So a freshly-constructed MeterModel reports active slice 0, but a cleared (post-disconnect) MeterModel reports -1. Functionally harmless because clear() always runs on disconnect before any TX activity could plausibly target slice 0, but the inconsistency is worth tightening.

Suggested fix

One-line change in the header:

int m_activeTxSlice{-1};

Then either:

• Drop the matching assignment from clear() (now redundant), or
• Leave both for symmetry with the rest of clear()'s "reset to default" pattern.

Either is fine. Whichever reads cleaner — I'd leave both for symmetry.

Why this is a good-first-issue

• One-line edit
• No tests need updating (existing tests that call setActiveTxSlice(0) already pass)
• Build + run ./build/meter_model_test to verify, no behavior change

cc @jensenpat — flagged this during review of #2073, didn't want to block the merge over it.