WezTerm/ConPTY on Windows drops Shift+letter keypresses entirely when
Kitty keyboard protocol flag 4 (report alternate keys) is set. Fall
back to flag 1 (disambiguate only) on Windows so shifted printable
keys are delivered as raw characters instead of being silently eaten.
Also adds a defensive SHIFT_MAP fallback in decodeKittyPrintable for
terminals that send CSI-u sequences with the shift modifier but omit
the shifted_key secondary codepoint.
Gergely Jutasi
91be0eba77