On Windows the constructor flag bitmask
(QWidget(parent, Qt::Window | Qt::FramelessWindowHint)) is sometimes
ignored — the native title bar still gets drawn.  Calling
setWindowFlags() with the same flags AFTER construction (before show())
forces the Windows platform plugin to honour the hint reliably across
Qt versions.

Symptoms reported on Windows: applet pop-outs still framed, and
panadapter pop-out crashing because the layout (QSizeGrip + GPU
spectrum widget) was wired for frameless but the actual window came
up framed.

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

…OS only)

FramelessWindowHint on Windows is unreliable — the constructor flag
bitmask is sometimes ignored so the native title bar still gets drawn,
and combined with QRhiWidget reparenting (the GPU spectrum) it
triggers a crash on panadapter pop-out.

Walk it back to Q_OS_WIN-guarded native frames everywhere.  Linux and
macOS still get frameless pop-outs with QSizeGrip resize and
startSystemMove drag — same behaviour as before this commit.  Windows
goes back to native chrome: native title bar moves the window, native
edges resize it, no QSizeGrip.

The × hide-on-float behaviour stays platform-independent — still good
UX even with a native title bar, since ↩ does the same thing.

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

…-pop crash)

Skip installEventFilter on PanadapterApplet's title-bar widget on
Windows.  The filter only exists to support startSystemMove drags on
frameless pop-outs (Linux/macOS); Windows keeps its native frame and
doesn't need it.

Side effect of installing the filter on Windows: title-bar mouse press
fired emit activated(panId) → PanadapterStack::setActivePan, a code
path v0.8.22 never exercised on title-bar clicks.  On a floating
panadapter this destabilised the second float→dock→re-float cycle and
crashed on re-pop.

Behaviour on Windows now matches v0.8.22 exactly for the panadapter
pop-out path.

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

…auses re-pop crash)"

This reverts commit 890cbb9.

…inux+macOS only)"

This reverts commit 8713720.