A repo with past, settled, and planned docs still has no answer for in-flight

Docs set had history (the past), a decision log (what is settled), and a build plan (what is next) — and no file answering what is being built RIGHT NOW. That gap is measurably expensive with parallel agents: two independently claimed the same sequential ID in an append-only log, and a third implemented decisions from a proposal still in draft, because nothing told either what the others were doing. Added an in-flight ledger listing every open PR, the choice it made, what it rejected, and what is broken and unfixed — plus a per-branch ID allocation table with the unclaimed ranges spelled out and an instruction to update it in the same commit. Two design points that make it work rather than rot: it says explicitly when to delete each section and when to delete the whole file (a ledger of nothing is worse than none, because readers trust it), and it records WHY the tempting fix is wrong, not just that it is — e.g. one branch existed to renumber off an ID collision, so a keep-both-sides conflict resolution reintroduces the collision it fixes.