v1.12 — Check tells you how long it took

From a field report (a two-stack project that adopted v1.7): the split between fast and full is
decided on step durations, and nothing in ANEW measured them.

• scripts/check prints <== <step> (n s) after every step (red ones too) and the total in the
  green line: CHECK GREEN (full, 14 steps, 1080 s). date +%s, no bc; where the clock gives
  no number, times are left out and the run still counts. The ==> <step> lines and the
  CHECK GREEN (<profile>, n steps / CHECK FAILED (<profile>) at step: prefixes are unchanged.
• docs/testing.md, Two speeds: "~a minute" is a per-step threshold, not a fast total; when fast
  grows too long, drop lint, then formatting, then unit tests. New rule 4: split a test step by a
  selector (category, trait, tag, namespace) and its inverse, never by a list — a test added
  later then still runs in one profile. New rule 5: decide on the median of at least 3 runs.
• prompts/bootstrap.md (3d) applies rules 4 and 5 at the gate.
• scripts/selftest checks that durations are present (never their value) and that a missing
  clock leaves them out.

Upgrading

scripts/check (behavior, for copies you extended): time each step with date +%s and print
<== <step> (n s) after it, red or green; append , <total> s inside the green line; print no
time when date +%s is not a number. Anything that parses the green line must accept the extra
field. docs/testing.md: Two speeds rule 3 (per-step threshold, removal order), new rules 4 and 5.
prompts/bootstrap.md 3d: selector split, median of 3. Full diff: v1.11...v1.12