Refactor docs/performance.md per librarian routing rule

docs/performance.md grew to 914 lines because dated experiments and
design analyses kept getting appended instead of routed to
docs/archive/ and docs/research/ as AGENTS.md prescribes. The
oversize check from librarian Stage 1 surfaced the file; this commit
acts on that finding by extracting the parts that belong elsewhere
and trimming the source to a focused current-state reference.

Extracts (verbatim from the original prose, with cross-link headers
and a brief routing note added at top):

- docs/archive/deep-cfr-performance-experiments-2026-05-07.md
  bundles torch.compile (regression), AMP (regression), GPU forward
  profiling (decision support), and Option B interleaved traversal
  (pass) — same date, same theme.
- docs/research/batched-traversal-inference-decision.md captures the
  durable A vs B vs C rationale with a closing "Outcome" pointer to
  the post-bench archive doc.
- docs/archive/post-a-optimization-calculus-2026-05-07.md preserves
  the forward-looking sequencing recorded pre-bench.
- docs/archive/option-a-bench-result-2026-05-07.md preserves the
  regression diagnosis and re-enable criteria.

docs/performance.md is now 345 lines, holds sections 1–9 (current
runtime / bottleneck / device / AMP status / batching / eval /
TensorRT / priorities), and ends with a "See Also" linking the four
extracts.

Also reworded the AGENTS.md soft-cap rule from a bare "~500-line
soft cap" to clarify the intent: the cap is a *routing trigger* (is
content piling up that should live in archive/research?), not a
split mandate. Reduces the risk of future agents shredding a useful
doc just to satisfy a number.

scripts/librarian.sh now exits 0 against the working tree.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

AGENTS.md

@@ -378,7 +378,10 @@ contention slows both unevenly and breaks the comparison.
 - archive 본문 복붙 금지 — 대신 `Source:` 링크 + distill.
 - `file.py:NN` 인용은 작성 시점에 `rg`로 검증.
 - 한 주제 한 파일 — `foo-v2.md` 만들지 말 것.
-- 파일당 ~500줄 soft cap.
+- 파일당 ~500줄 soft cap — 강제 분할이 아니라 "다른 위치(archive/research)로
+  가야 할 내용이 누적됐는지" routing 점검 트리거. 초과 시 dated 실험은
+  `docs/archive/`로, 항구적 분석은 `docs/research/`로 보내고 본 파일은
+  현재 상태 reference만 남긴다.
 
 ## Notes For Future Agents