fix: properly reset cost limit tracking when user clicks "Reset and Continue"

[roomote]

Summary

This PR fixes issue #6889 where the cost limit was not being properly reset when users clicked "Reset and Continue" after hitting the auto-approved cost limit.

Problem

When a user hit the cost limit and clicked "Reset and Continue", the cost would immediately trigger the limit again on the next API request because the total cost was still being calculated from all messages in the conversation history.

Solution

The fix tracks the message index at the time of cost reset and only calculates costs from messages after that reset point. This ensures that:

• When users approve continuing after hitting the cost limit, only new costs are counted
• Multiple resets are handled correctly
• The behavior matches user expectations

Changes

• Added costResetMessageIndex tracking in AutoApprovalHandler
• Modified cost calculation to only include messages after the reset point
• Updated the reset method to also reset the cost tracking index
• Added comprehensive tests to verify the fix works correctly

Testing

• ✅ All existing tests pass
• ✅ Added new tests specifically for cost reset functionality
• ✅ Verified multiple cost resets work correctly

Fixes #6889

---

Important

Fixes cost limit reset issue in AutoApprovalHandler by tracking message index at reset and updating cost calculations accordingly.

• Behavior:
  • Fixes cost limit reset issue in AutoApprovalHandler by tracking lastResetMessageIndex.
  • Cost calculations now only include messages after the reset point.
  • Supports multiple resets and matches user expectations.
• Implementation:
  • Adds lastResetMessageIndex to track message index at reset in AutoApprovalHandler.
  • Modifies checkRequestLimit() and checkCostLimit() to use messages after reset.
  • Updates resetRequestCount() to reset lastResetMessageIndex and cost tracking.
• Testing:
  • Adds tests in AutoApprovalHandler.spec.ts for cost reset functionality.
  • Verifies correct behavior for multiple resets and floating-point precision handling.

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[roomote]

Reviewing my own code is like debugging in production - technically possible but morally questionable.

[daniel-lxs]

LGTM

[mrubens]

This logic feels a lot messier than it needs to be. It seems like we should use the same approach and methods for tracking number of requests and total cost.

[hannesrudolph]

@mrubens Can you please take a look?