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>

docs/plans/librarian.md

@@ -165,11 +165,29 @@ deterministic detection:
   and derived research notes; LLM should decide whether two passages
   are the *same idea* vs the *same evidence*.
 
-Open Stage 1 finding to address: `docs/performance.md` at 914 lines.
+## Stage 1 finding closed
+
+`docs/performance.md` 914-line oversize finding is resolved by
+routing the dated experiments and design analysis out of the file:
+
+- `docs/archive/deep-cfr-performance-experiments-2026-05-07.md` —
+  `torch.compile`, AMP, GPU-forward profiling, Option B (4 sub-experiments).
+- `docs/research/batched-traversal-inference-decision.md` —
+  durable A/B/C design rationale.
+- `docs/archive/post-a-optimization-calculus-2026-05-07.md` —
+  forward-looking sequencing recorded pre-bench.
+- `docs/archive/option-a-bench-result-2026-05-07.md` —
+  bench regression + structural-ceiling diagnosis.
+
+`docs/performance.md` trimmed to 345 lines and now points at the
+extracts via a "See Also" section. AGENTS.md soft-cap rule reworded
+to clarify it is a *routing trigger*, not a split mandate.
 
 ## Next Concrete Step
 
-Address the open Stage 1 finding by splitting `docs/performance.md`
-into sub-topic notes under `docs/research/` (and dated archive
-entries where appropriate). Sketch the split as a 1-page sub-plan
-before doing the actual move so we don't shred a useful document.
+Stage 2 — LLM judgment dispatcher. Read `librarian-<timestamp>.json`
++ relevant doc bodies, route to `LIBRARIAN_LLM={claude|codex|gemini}`
+with `scripts/librarian-prompt.md` as system prompt, emit a unified
+diff under `runs/tmp/librarian-<timestamp>.patch`. Initial use cases:
+research-note drafts for promotable archive entries, MEMORY.md drift
+fixups, duplicate-doc merge proposals.