HL2: setBandFilter() queues a redundant CONFIG one-shot that can put a stale sample rate on the wire

Summary

MetisClient::setBandFilter() queues a copy of m_ccConfig into m_oneShot. That one-shot is redundant, and because it is a snapshot, it can put a stale config on the wire.

Found during review of #4503 (not a regression from it — the one-shot is added by that PR, but the effect is bounded and was not worth blocking on).

Why it is redundant

buildNextControlPacket() builds every EP2 frame as:

auto pkt = ep2Packet(m_txSeq++, withMox(m_ccConfig, keyed), withMox(b, keyed));

Bank A is live m_ccConfig on every single frame. The one-shot only ever populates bank B. So the stated purpose — "a band change moves the NCO and the filter in the same gesture, don't wait for the round robin" — is already satisfied by bank A without the push.

Why it can be stale

Bank B is applied after bank A, so when the two disagree the snapshot wins for that frame:

1. setBandFilter(X) pushes snapshot S = ccConfig(rate_old, numRx, X).
2. setSampleRate(rate_new) rebuilds m_ccConfig = ccConfig(rate_new, numRx, X).
3. Next frame: bank A = rate_new, bank B = S = rate_old. The radio ends on rate_old.

Bank A re-asserts the truth on the following frame, so the visible effect is one EP2 frame (~1 ms) of stale DDC rate. Small, but it is a real transient the code does not intend.

Additionally, m_oneShot is not cleared in start() (it is cleared nowhere). Hl2Backend::applyBandFilter() has no m_connected guard and m_metis outlives a disconnect, so a snapshot queued while disconnected can replay on the next session's first frames.

Suggested fix

Delete the m_oneShot.push_back(m_ccConfig) in setBandFilter(). Bank A already does the job, and removing the push eliminates the staleness with it.

If the push is kept for some reason not visible here, then m_oneShot.clear() belongs in start() alongside the other per-session resets (m_txSeq, m_roundRobin, m_haveRxSeq, m_drops, m_linkUp).

Start at MetisClient::setBandFilter() and trace buildNextControlPacket() to confirm that bank A already sends the live configuration. Inspect start() and the m_oneShot lifecycle, then remove the redundant queued snapshot. Done means a band change still reaches the control packet promptly without replaying a stale sample rate, with the relevant C++ tests or build passing.