fix(runner): stop reporting context-window size as a run's token usage - #5710

2 599 tests  +974   2 526 ✅ +929   36s ⏱️ +4s
    1 suites ±  0      73 💤 + 45 
    1 files   ±  0       0 ❌ ±  0 

Results for commit 39fb38e. ± Comparison against earlier commit ab1460e.