Budget Management - Limit token sizes

Some diffs can be quite large. Sometimes those large diffs include changes that are not relevant to a code review, like dependency updates.

Sending these diffs to OpenAI will consume credits unecessarily.

Implement a relief valve and budget manager for token usage.
The ability to set a token limit.

This article from Microsoft introduces a strategy for prompt compression with no loss.

https://arxiv.org/abs/2310.05736

No files or tests are named. Start by locating the code path that sends diffs to OpenAI and review how token usage is currently measured; define the token-limit behavior and verify that oversized or irrelevant diffs stay within the configured budget.

Written by the indexing model from the issue text.