Single card generation option for Write and Rewrite

## As an author I want to generate text that continues or rewrites my work while minimising the number of words that I am paying to generate. Preferred behaviour: When I select a "write" function or a "rewrite" function, a single card is generated, creating 1 complete written option, so if I wanted to generate a new 300 words or rewrite 300 words, any function I use generates 300 words. If I want to experiement by changing a small variation, I use another 300 words, if I want to make a second change I use another 300 words. This might mean I use 900 words to improve 300 words. Incentivising experimentation and supporting my ability to use the platform on longer projects.