docs: fold Review 2 into the FSRS spec (Response 2)

Review 2 (Codex) flagged three blockers in my Response 1, and two were mine to own. I'd reversed DRILL_CARD_WEIGHT: I described SM as multiplying the interval when it actually divides the delta, so weight 2 means more frequent review, not less. And I'd locked a quality mapping that both claimed to honor org-drill-failure-quality and hard-coded a fixed table.

Craig's calls: FSRS matches the existing SM/Simple8 delta interpolation for weight, and honors org-drill-failure-quality for the Again boundary with a fixed Hard/Good/Easy sub-mapping. I fixed both throughout the spec and grounded each claim in the cited org-drill.el line so the description can't drift again.

I also reframed the status to "Needs research" with the three real prerequisites stated honestly (pin the py-fsrs source, cross-check the equations, generate the reference vectors), fixed DRILL_LAST_REVIEWED ownership back to the shared reschedule flow, and noted that fsrs has to join the algorithm defcustom and the safe-local whitelist. The review file is committed alongside the spec as the audit trail.

The spec is still not implementation-ready, and now says so plainly.

0 files changed, 0 insertions, 0 deletions