Emits a timing block (durations, phase walls, total) before the summary
line; the ok/FAIL and 'all N passed' contract is unchanged and the only
consumer (make's exit-code gate) is unaffected. Measured baseline at
4ff79bf: 211.6s wall, 990-995 self-compile gates = 87% of wall — the
content-keyed skip tier (T1) targets exactly that block. Baseline data:
.ai/testperf-baseline.md.