Report unavailable protocols and services; send combos as real keys

Diagnostics collects what this session doesn't allow, logs it, and lists
it in the settings panel (with a dot on the gear): KWin not launching
sloposk as its keyboard (detected by WAYLAND_SOCKET, since KWin offers the
input-method global to every client), fake input missing or too old,
org.kde.keyboard unreachable, and the D-Bus control name taken.

Modifier combos go through fake input even in text fields: KWin drops
the input method's modifier mask for most clients, so Ctrl+A typed "a".

The desktop file is generated with an absolute Exec, which KWin needs to
match it: one for the installed binary, one for the build's.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/CMakeLists.txt

@@ -26,6 +26,7 @@ qt_add_library(sloposk_core STATIC
     window/WindowSettings.h window/WindowSettings.cpp
     settings/DebouncedStore.h settings/DebouncedStore.cpp
     settings/Settings.h settings/Settings.cpp
+    diagnostics/Diagnostics.h diagnostics/Diagnostics.cpp
 )
 
 # QML lives in the top-level qml/ dir; alias each file so the module sees it at its root.
@@ -39,6 +40,7 @@ set(SLOPOSK_QML_FILES
     SectionHeader.qml
     SettingsButton.qml
     SettingsPanel.qml
+    ProblemList.qml
     ToggleRow.qml
     SliderRow.qml
     Theme.qml
@@ -68,6 +70,7 @@ target_include_directories(sloposk_core PRIVATE
     ${CMAKE_CURRENT_SOURCE_DIR}/input
     ${CMAKE_CURRENT_SOURCE_DIR}/layout
     ${CMAKE_CURRENT_SOURCE_DIR}/settings
+    ${CMAKE_CURRENT_SOURCE_DIR}/diagnostics
 )
 target_link_libraries(sloposk_core PUBLIC Qt6::Quick PkgConfig::XKB)
 
@@ -77,6 +80,7 @@ qt_add_executable(sloposk
     main.cpp
     app/DevHooks.h app/DevHooks.cpp
     app/DBusControl.h app/DBusControl.cpp
+    app/Checks.h app/Checks.cpp
     app/QuitOnSignal.h app/QuitOnSignal.cpp
     app/SystemLayouts.h app/SystemLayouts.cpp
     backend/InputMethodProtocol.h
@@ -107,4 +111,13 @@ target_link_libraries(sloposk PRIVATE
 )
 
 install(TARGETS sloposk)
-install(FILES ${PROJECT_SOURCE_DIR}/data/org.sloposk.keyboard.desktop DESTINATION ${CMAKE_INSTALL_DATADIR}/applications)
+# KWin grants restricted protocols by matching Exec to the absolute executable
+# path. One file runs the installed binary; the other the build's, for development.
+set(SLOPOSK_EXEC ${CMAKE_INSTALL_FULL_BINDIR}/sloposk)
+configure_file(${PROJECT_SOURCE_DIR}/data/org.sloposk.keyboard.desktop.in
+               ${CMAKE_CURRENT_BINARY_DIR}/install/org.sloposk.keyboard.desktop @ONLY)
+set(SLOPOSK_EXEC ${CMAKE_CURRENT_BINARY_DIR}/sloposk)
+configure_file(${PROJECT_SOURCE_DIR}/data/org.sloposk.keyboard.desktop.in
+               ${CMAKE_CURRENT_BINARY_DIR}/org.sloposk.keyboard.desktop @ONLY)
+install(FILES ${CMAKE_CURRENT_BINARY_DIR}/install/org.sloposk.keyboard.desktop
+        DESTINATION ${CMAKE_INSTALL_DATADIR}/applications)