EPIC APR-LOOKAHEAD-001: rolling look-ahead workers (one per each of the next 3 trains) #4540

Spec: APR-LOOKAHEAD-001 v1.1 (operator directive 2026-09-27); staged at /mnt/nvme-raid0/cop-inbox/handoff/APR-LOOKAHEAD-001.md until LA-00 commits it to docs/specifications/.
Rows LA-00..LA-08 are sub-issues. K̂=455, K=520, andon at 415. Implementer: la-impl. Slots: L1 kreg (0.71), L2 la-72, L3 la-73.

Rows (folded as checklist lines, ISSUE-TREE-001, aprender-wtix-even)

• LA-00: commit spec + cop-state/lookahead.json schema + docs/lookahead/{0.71,0.72,0.73}.md skeletons #4541 LA-00: commit spec + cop-state/lookahead.json schema + docs/lookahead/{0.71,0.72,0.73}.md skeletons
• LA-01: fill slots + record 0.72/0.73 theme ruling and §2a exit criteria in 06x-release-schedule.md #4542 LA-01: fill slots + record 0.72/0.73 theme ruling and §2a exit criteria in 06x-release-schedule.md
• LA-02: cop tick checks I1–I4 and respawns dead slots from the handoff file #4543 LA-02: cop tick checks I1–I4 and respawns dead slots from the handoff file
• LA-03: standing prompt docs/prompts/lookahead-worker.md (§7) #4544 LA-03: standing prompt docs/prompts/lookahead-worker.md (§7)
• LA-04: enforce look-ahead open-PR budgets + queue ordering behind train N #4545 LA-04: enforce look-ahead open-PR budgets + queue ordering behind train N
• LA-05: readiness gate (DoR N+1, N+2/N+3 checks) in the hourly report + train-start latency #4546 LA-05: readiness gate (DoR N+1, N+2/N+3 checks) in the hourly report + train-start latency
• LA-06: §5 budget pause ladder for look-ahead slots #4547 LA-06: §5 budget pause ladder for look-ahead slots
• LA-07: atomic rotation at crates.io publish; spawn N+4 before announce #4548 LA-07: atomic rotation at crates.io publish; spawn N+4 before announce
• LA-08: ruling request — offer the slot model to Tier-2 repos (optional) #4549 LA-08: ruling request — offer the slot model to Tier-2 repos (optional)

owner: la-0.72 (set 2026-10-09 by clerk aprender-3e for cop aprender-13: works child #4527 (QM-09))