Adds the optional Apollo-era Quindar tones to MOX/PTT on phone modes.
Tone style (default) plays a 2525 Hz sine intro then a 2475 Hz outro,
each 250 ms with a 5 ms cos² ramp; Morse style sends "K" on engage
and "BK" on disengage at a configurable WPM/pitch.  Ships disabled by
default; opt-in via the new QUIN chip in the channel strip's Final
Output Stage panel (right-click for the style/freq/WPM editor).

DSP (`ClientQuindarTone`) is lock-free atomic-driven and inserted
between PC mic gain and the final brickwall limiter, so the tone is
unprocessed by the user's DSP chain but still bounded by the
configured ceiling.  A dedicated `QuindarLocalSink` mirrors the same
audio to the operator's local output device — Quindar must always be
locally audible whenever it's overlaying the TX stream.

`TransmitModel::requestPttOn/Off` is the new single entry point for
PTT requests.  The MOX button and the TCI hardware-PTT path both
route through it; the coordinator runs the engage/disengage state
machine, defers `xmit 0` by the outro duration so the tone actually
makes it on the air, and coalesces a re-engage during the outro
window so the user doesn't feel a dead zone.  CW / digital modes
bypass Quindar entirely via the phone-mode gate.

The QUIN chip flashes bright while a tone is playing — signal-driven
via the new `TransmitModel::quindarActiveChanged` rather than a
polling timer.  Test harness covers phase transitions, frequency
content (Goertzel), Morse K/BK timing, envelope ramp, level matching,
coalesce semantics, and disabled bypass (19 tests, all pass).

Quindar settings are intentionally excluded from Channel Strip
preset capture — they're a PTT-time stylistic choice, not voice
shaping; preset recall shouldn't silently start signing off the
operator's transmissions.

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>