…). Principle IX.

PR #3031 (TX waterfall scroll-rate parity) removed the debt-gated FFT row
emission and per-frame linear-power accumulator from
SpectrumWidget::pushWaterfallRow but intentionally left the supporting
state in place to keep the behavioural-fix diff focused. This commit
removes that now-dead state:

- m_lastFftRowMs, m_lastFftFrameMs, m_fftRowDebtMs (pacing timestamps for
  the removed debt gate)
- m_fftAccumPower, m_fftAccumCount (per-bin linear-power accumulator for
  the removed inter-frame averaging)
- SpectrumWidget::resetFftWaterfallAccumulator() and its 4 call sites in
  setWfLineDuration(), setTransmitting(true), setTxWaterfallSlice(), and
  clearTxWaterfallSlice() — each was a bare statement with no surrounding
  logic to untangle

Grep across the codebase confirmed the only writes to these members were
inside the reset function itself, and no read sites remained anywhere.
Pure dead-code removal — 26 LOC net, zero behavioural change. The TX
waterfall scroll-rate parity verified by #3031 covers the path.

Blast radius: removed symbols are private to SpectrumWidget; the
PreToolUse hook flagged risk_score=0.291 against SpectrumWidget.h/.cpp as
whole TUs (high-bw MainWindow callers exist) but those callers do not
touch the removed private members — confirmed by grep before edit.

…). Principle IX. (#3040)

## Summary

Fixes #3038

### What was changed

cleanup(spectrum): remove dead FFT accumulator state after #3031
(#3038). Principle IX.

### Files modified

- `src/gui/SpectrumWidget.cpp`
- `src/gui/SpectrumWidget.h`

```
 src/gui/SpectrumWidget.cpp | 14 --------------
 src/gui/SpectrumWidget.h   | 12 ------------
 2 files changed, 26 deletions(-)
```

---
Generated by AetherClaude (automated agent for AetherSDR)

---
<sub>🤖 aethersdr-agent · cost: $10.0359 · model: claude-opus-4-7</sub>

Co-authored-by: aethersdr-agent[bot] <273844287+aethersdr-agent[bot]@users.noreply.github.com>

## Summary

Fix TX waterfall scrolling visibly slower than RX (~3x slower in
practice) after PR aethersdr#3019 landed.

## Root cause

`pushWaterfallRow` (FFT-derived row path, sole TX waterfall source
post-aethersdr#3019) was gating row emission to one row per `m_wfLineDuration`
(100 ms by default) on the premise that RX native tiles also arrive at
line_duration cadence.

They don't. Native tiles arrive at the radio's FFT rate (~30 Hz on this
fleet) and `updateWaterfallRow` pushes one row per tile with no rate
gate. So RX = ~30 rows/sec and TX = ~10 rows/sec → 3x perceptual
slowdown.

Pre-aethersdr#3019 this was masked: with show-tx-in-waterfall on, native tiles
*also* ran during TX, filling the cadence regardless of whether the FFT
gate let a row through. aethersdr#3019 correctly stopped the double-advance — and
that exposed the underlying pacing-assumption bug from aethersdr#2666.

## Fix

Emit one row per FFT frame from `pushWaterfallRow`, matching the
native-tile behaviour exactly. The intermediate-frame linear-power
accumulator becomes unnecessary (no intermediates to combine when each
frame is its own row); intra-frame bin interpolation is now in dBm
space, consistent with `updateWaterfallRow`.

## What I left alone

State members (`m_fftRowDebtMs`, `m_lastFftFrameMs`, `m_fftAccumPower`,
`m_fftAccumCount`) and `resetFftWaterfallAccumulator()` are now unused
but left in place to keep this diff focused on the behavioural fix.
Cleanup PR can remove them.

## Diagnostic evidence

Probe instrumentation in `pushWaterfallRow` and `updateSpectrum`
confirmed before the fix:
- FFT frames arrive at ~30 Hz during both RX and TX (~33 ms intervals,
no radio-side throttle)
- `pushWaterfallRow` was called ~270 times in a 9-second TX window, but
only emitted 92 rows (~10 rows/sec, matching the gated cadence)

After the fix, every FFT frame produces a row → ~30 rows/sec, parity
with RX.

## Stats

- 1 file, +22 / -55
- No new flat-key AppSettings (Principle V N/A)
- MeterSmoother N/A (no meter code)

## Test plan

- [x] Local build clean
- [x] Visual confirmation by Jeremy on FLEX-8600 USB at 14.265 MHz: TX
waterfall scroll now matches RX speed
- [ ] CI: build + check-paths green; check-windows skipped (no build
paths changed) — this PR doesn't touch MainWindow.cpp so aethersdr#3028's new
filter doesn't fire

## Checklist

- [x] No new flat-key `AppSettings`
- [x] All meter UI uses `MeterSmoother` (N/A)
- [x] Documentation updated if user-visible behavior changed (release
notes will mention TX waterfall rate fix)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

…3031 (aethersdr#3038). Principle IX. (aethersdr#3040)

## Summary

Fixes aethersdr#3038

### What was changed

cleanup(spectrum): remove dead FFT accumulator state after aethersdr#3031
(aethersdr#3038). Principle IX.

### Files modified

- `src/gui/SpectrumWidget.cpp`
- `src/gui/SpectrumWidget.h`

```
 src/gui/SpectrumWidget.cpp | 14 --------------
 src/gui/SpectrumWidget.h   | 12 ------------
 2 files changed, 26 deletions(-)
```

---
Generated by AetherClaude (automated agent for AetherSDR)

---
<sub>🤖 aethersdr-agent · cost: $10.0359 · model: claude-opus-4-7</sub>

Co-authored-by: aethersdr-agent[bot] <273844287+aethersdr-agent[bot]@users.noreply.github.com>