System-tray handling overhaul (closes #334) - #574

…mule-project#334)

When DoMinToTray is enabled and the user clicks the yellow minimize
button on macOS, the previous behaviour left a Dock thumbnail of the
window even though the tray icon was meant to be the recovery
surface. Plain Show(false) cannot remove the Dock thumbnail (the
miniaturize animation completes regardless) and Iconize(false)
re-shows the window via Mac's deminiaturize-then-orderFront sequence.

Toggle NSApp's activation policy instead. While the main window is
hidden via the tray flow, set NSApplicationActivationPolicyAccessory
— that removes the Dock icon entirely (and any in-flight Dock-tile
target), leaving the NSStatusItem as the only surface. When the user
un-hides via the tray click or menu, restore
NSApplicationActivationPolicyRegular and call activateIgnoringOtherApps:
so the window comes to the foreground above other apps.

Implementation:

* `src/MacAppHelper.{h,mm}` — minimal Obj-C++ helper exposing
  `mac_set_accessory_mode(bool)` via `extern "C"`. AppKit is pulled
  in transitively by wxWidgets so no extra `-framework` line is
  needed.
* `cmake/source-vars.cmake` — appends `MacAppHelper.mm` to
  `GUI_SOURCES` only when `APPLE`.
* `src/amuleDlg.cpp::OnMinimize` — drop the Linux-only "evil hack"
  filter on macOS (`wxFindWindowAtPoint` returns NULL during the
  yellow-button transition there, silently skipping the hide-to-tray
  branch) and call `mac_set_accessory_mode(true)` before `Show(false)`
  on the iconize path.
* `src/MuleTrayIcon.cpp::DoShowHide` — call
  `mac_set_accessory_mode(true)` when hiding via the tray gesture,
  and `mac_set_accessory_mode(false)` before `Show(true)` when
  un-hiding.

Linux and Windows code paths unchanged.

…mule-project#334)

HideOnClose used to consume every path that reached CamuleDlg::OnClose
with a vetoable wxCloseEvent — including the tray-icon Exit menu,
Cmd+Q on macOS, and the Dock right-click → Quit. Explicit quit
requests should always quit; HideOnClose should govern only the red
close-button gesture.

Three signals now bypass the hide-on-close veto branch:

* `Close(true)` (force=true ⇒ CanVeto()==false) — already used by the
  wxID_EXIT handler (Cmd+Q / menu Quit).
* `CMuleTrayIcon::DoExit` was passing `force=false`; now sets a new
  `IsQuitting()` flag and calls Close() so the confirm-exit prompt
  can still run if enabled.
* `CamuleGuiApp::OnQueryEndSession` sets `IsQuitting()` before
  forwarding to wx's default session-end handling. Captures the Dock
  right-click → Quit path on macOS, which otherwise looks identical
  to a regular close to the OnClose handler.

The IsQuitting flag lives on CamuleAppCommon so both the monolithic
CamuleApp and the remote-GUI CamuleRemoteGuiApp expose the same
accessors. CamuleDlg::OnClose's hide branch is now
`hideOnClose && evt.CanVeto() && !theApp->IsQuitting()`, and a
confirm-exit veto resets the flag so a later close-button click
respects HideOnClose again.

In the same spirit, the prefs panel no longer greys out the
"Show confirmation on exit" checkbox when HideOnClose is on — they're
orthogonal now that the clean exit paths (tray Exit, Dock Quit) can
still ask for confirmation via the OnClose veto.

…howGUI (amule-project#334)

Cross-platform polish around the tray-icon code paths:

* **Iconize-aware menu and DoShowHide** — `theApp->amuledlg->IsShown()`
  is true even when the window is iconized to Dock/taskbar, which let
  the menu offer "Hide aMule" in those states; clicking would then
  Show(false) the already-hidden window, destroying the only recovery
  surface. Track iconize separately via a `m_iconized_logical` flag
  set from `wxIconizeEvent::IsIconized()` (reliable cross-platform —
  unlike `wxFrame::IsIconized()` which can lag on wxGTK), and require
  `IsShown() && !IsTrayLogicallyIconized()` for the menu label and
  the DoShowHide branch.

* **Iconize(false) before Show(true)** on every platform when
  un-hiding via the tray — without this a previously-iconized window
  would come back as a taskbar-iconized entry, not a real restored
  frame.

* **Single-left tray click toggles the window on Windows** —
  EVT_TASKBAR_LEFT_UP wired to SwitchShow. Matches the convention
  of Discord/Slack/Telegram/qBittorrent. macOS NSStatusItem opens
  its menu on single-click via its own default.

* **`GuiEvents::ShowGUI` brings the window back from any hidden
  state** — running instance picks up the RAISE_DIALOG signal from
  duplicate-launch (pinned-shortcut click etc.) via ED2KLinks polling
  and lands here. Previous implementation only did Iconize(false);
  add Show(true) + Raise() + mac_set_accessory_mode(false) so a
  window hidden via HideOnClose / minimize-to-tray / accessory-mode
  also restores.

* **SNI tray menu refresh on every show/hide** — SNI menus are built
  once and held; expose RebuildMenu() publicly and call it from a new
  EVT_SHOW handler so the "Show aMule"/"Hide aMule" entry stays in
  sync after HideOnClose / programmatic Show(false). Also call it
  from OnMinimize so iconize state changes refresh the label.

The macOS Dock-toggle path from the previous commit still applies on
top — `mac_set_accessory_mode(true)` runs before Show(false), and
`mac_set_accessory_mode(false)` runs before Show(true).

…ct#334)

The Network tab's splitter had `SetSashGravity(0.5f)` set, which made
it the only one in aMule that proportionally re-laid-out children
when the parent window resized. On both Mac and Windows that
proportional recalculation also fired during the minimize/restore
reflow with transient parent dimensions, producing
`wxEVT_SPLITTER_SASH_POS_CHANGED` events with positions outside the
visible range — `OnSashPositionChanged` then stomped the saved
position with garbage that collapsed the log pane the next time the
window came back.

Two-part fix at the root cause:

* Drop `SetSashGravity(0.5f)` in `CServerWnd`'s constructor. The
  other amule splitters (Shared/Transfer/Messages) all use the
  default gravity (0.0) and don't suffer the layout-recalc storm —
  the Network tab now behaves the same way. UX implication: when the
  user resizes the main window, the server list keeps its height
  and the log pane absorbs the extra space (or shrinks), instead of
  the two sharing proportionally. Net positive — the server list is
  a finite enumeration that doesn't benefit from extra room, while
  the log pane does.

* Add a CHANGING/CHANGED protocol around sash persistence:
  `wxEVT_SPLITTER_SASH_POS_CHANGING` only fires while the user is
  actually dragging, so set a flag there; only persist the new
  position in `OnSashPositionChanged` when the flag is set, then
  clear it. Defensive — even if a future wx/GTK quirk fires CHANGED
  from a layout reflow again, we won't stomp the saved position.

…le-project#334)

Linux has two separate ways the tray-icon UX can silently fail; both
are gated at startup + in the prefs panel so users don't enable an
option that does nothing.

**No libayatana-appindicator3 at compile time.** When aMule is built
without the AppIndicator dep, wxTaskBarIcon falls back to the legacy
GtkStatusIcon backend that GNOME Shell dropped in 3.26 (Ubuntu's
default since 2017) and wlroots-based compositors never implemented
— the icon is silently invisible. CamuleApp::OnInit force-clears
UseTrayIcon at startup; PrefsUnifiedDlg disables the IDC_ENABLETRAYICON
checkbox with a tooltip pointing at libayatana-appindicator3 as the
rebuild dependency.

**Wayland session.** xdg-shell intentionally doesn't deliver
iconified-state notifications to clients (no signal exists per GTK
maintainers; wayland-protocols MR !201's xdg_toplevel.suspended is
neither universally supported nor a clean minimize proxy), so the
system minimize button cannot trigger our Show(false) hide-to-tray
path. Same gap is documented across qBittorrent #17265, Telegram
#2123, KeePassXC #6502, Slack/Element/Spotify — none have a fix
either. Force MinToTray off when running under a Wayland session
and disable the IDC_MINTRAY checkbox with a tooltip citing the
protocol limitation. The HideOnClose path still works fine on
Wayland (X button → Show(false) is reliable), so users who want
tray-only behaviour can still get it via that route.

Detection is via standard runtime env vars: WAYLAND_DISPLAY or
XDG_SESSION_TYPE=wayland marks the session as Wayland. Users who
want minimize-to-tray under Wayland can force XWayland by launching
`GDK_BACKEND=x11 amule` — the same workaround Discord users have
adopted — and our detection honours the env var by treating it as
X11. The prefs tooltip mentions the workaround so users discover
it without reading source.

…le-project#334)

The General prefs panel previously had:

    [ ] Prompt on exit
    [ ] Hide application window when close button is pressed
    [ ] Enable Tray Icon
    [ ] Minimize to Tray Icon

Hide-on-close and minimize-to-tray both depend on the tray-icon
master being enabled (the runtime gate force-clears them otherwise
and the prefs-panel live-gating greys both checkboxes when tray is
off). Showing the master switch after its dependents made the
relationship harder to see; move it above so the visual hierarchy
matches the gate hierarchy:

    [ ] Prompt on exit
    [ ] Enable Tray Icon
    [ ] Hide application window when close button is pressed
    [ ] Minimize to Tray Icon

Pure layout shuffle — no behavioural change, no string changes.