v0.6.7 — review lane timebox re-check, health clone.log pre-create, docs

Review lane (#79): run_with_watchdog() re-checks kill -0 immediately before marking a timeout, so a seat that already exited at the timebox edge is reported with its real exit code instead of 124; a truly hung seat still gets stop_seat_tree and 124. Behaviour note: a seat that exits at the boundary but leaves a live descendant is reported as 125 (not 124); the tree is still killed. Deterministic boundary test via a BASH_ENV fake clock.

Health lane: evidence/clone.log is pre-created so an unwritable evidence/ is reported as evidence-log-unwritable (not clone-failed); the second pgrep -g read in stop_remaining_tree is fail-closed (rc>1 → unconditional group KILL). Docs: Makefile detection is a test: target (test:= excluded); evidence-unwritable upgrades exit 0/3 to 1.

Evidence: PR #32 (completion record; Kimi/Grok/Opus GO), guard run https://github.com/caty-ai/alpha-nightshift/actions/runs/34046927692