fix(tui): pass fg prop to diff component for light mode support

Author: code-yeongyu

packages/opencode/src/cli/cmd/tui/routes/session/index.tsx

@@ -1604,6 +1604,7 @@ ToolRegistry.register<typeof EditTool>({
               showLineNumbers={true}
               width="100%"
               wrapMode={ctx.diffWrapMode()}
+              fg={theme.text}
               addedBg={theme.diffAddedBg}
               removedBg={theme.diffRemovedBg}
               contextBg={theme.diffContextBg}