[runtime] add context-sharing across chats with same tag

[signebedi]

After implementing tags in #5, we should add context sharing where the chat can see (up to a certain length) all of the content with the same tag, concatenated.

[signebedi]

There may need to be token limits that we impose on context variable. https://stackoverflow.com/questions/70060847/how-to-work-with-openai-maximum-context-length-is-2049-tokens

[signebedi]

In the end, we needed to stack the prior context onto the new question, per https://community.openai.com/t/how-do-you-maintain-historical-context-in-repeat-api-calls/34395/2.