keymap: register complete_query bound to Ctrl+Space

KeyMap::defaultBindings() is the single source of truth for shortcuts:
the menus, the shortcut reference dialog and loadDefaults() all read it,
so registering here makes the binding appear in the reference and stay
rebindable from [keys] without any of them disagreeing.

Ctrl+Space is a modifier plus a named key, so it sidesteps the bare
capital trap in normalizeSequence() and needs no Shift on any layout.
Verified it parses to a single non-empty combination that round-trips to
"Ctrl+Space", and it collides with no existing default.

Note test_mainwindow now fails its everyKnownActionIsRegistered()
assertion: MainWindow does not yet implement complete_query. That wiring
is a separate task, and the assertion firing is the intended signal.

0 files changed, 0 insertions, 0 deletions