Add xg_lfSmallLogFont (LOGFONTW) for small font management with backward compatibility

[Copilot]

Adds xg_lfSmallLogFont (LOGFONTW) as the internal representation for the small font setting, complementing the existing xg_szSmallFont string. Board rendering now uses xg_lfSmallLogFont directly. Font size remains dynamically computed from cell size — the LOGFONTW struct carries only face name and style properties, never size fields.

Changes

New global (XG_Settings.hpp, GUI.cpp)

• LOGFONTW xg_lfSmallLogFont = {} — always has lfHeight = lfWidth = 0; size is computed at draw time in XgCreateSmallFont()

Drawing (XWordGiver.cpp)

• XgCreateSmallFont() now mirrors XgCreateNormalFont(): starts from xg_lfSmallLogFont, overrides size fields dynamically, falls back to defaults for weight/quality/charset if unset

LOOKS file I/O (GUI.cpp, XG_SettingsDialog.cpp)

• Import: reads SmallFont (compat) then SmallLogFont (hex-encoded LOGFONTW via XgHexToBin); SmallLogFont wins if valid, otherwise falls back to SmallFont face name
• Export: writes both SmallFont and SmallLogFont (XgBinToHex) every time

Registry I/O (GUI.cpp)

• Reads/writes SmallLogFont as a struct (size fields zeroed on write, same pattern as CellLogFont)

Settings dialog (XG_SettingsDialog.cpp)

• On OK: syncs xg_lfSmallLogFont.lfFaceName from edt2 alongside xg_szSmallFont
• Font chooser for small font (case 1): initializes ChooseFontW from xg_lfSmallLogFont instead of bare face name
• DoImportLooks / DoExportLooks: reads/writes SmallLogFont in addition to SmallFont

Existing LOOKS files with only SmallFont continue to work unchanged — xg_lfSmallLogFont is populated from the face name string as a fallback.