fix: token total formula missing output_tokens from last turn

[Deepak8858]

Description

Corrects the token calculation in extract_usage_tokens() and quick_token_estimate() to include output_tokens from the last assistant turn, matching the formula used in Claude Code.

Changes

• Updated extract_usage_tokens() to include output_tokens in total.
• Updated quick_token_estimate() to include output_tokens in the final return value.

Fixes #36

[junaidtitan]

Thanks for the PR @Deepak8858! This is the exact right fix — we actually shipped this same change in v1.4.0 (commit 2f97f81). Both extract_usage_tokens() and quick_token_estimate() now include output_tokens in the total.

Closing since it's already merged, but appreciate you spotting it and taking the time to submit. If you find other issues feel free to open a PR — contributions are welcome!