[codex] Add R3 evaluator Phase 4 audit handoff

docs/audit/r3-evaluator-phase4-audit-handoff.md

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+# R3 Evaluator Phase 4 Audit Handoff
+
+**Status:** handoff packet, 2026-05-06. Docs/audit only. This packet
+does not implement evaluator behavior, edit substrate declarations, touch
+generated manifests, alter CI, or change runner code.
+
+**Phase 3 anchor:** PR #1838 merged on 2026-05-06 as the
+`docs/audit/r3-evaluator-pr-1275-1500-debt-sweep.md` receipt for the
+#1275-#1500 evaluator slice. That receipt is the source for the live queue
+below; this file turns it into the next actionable audit shape.
+
+**Sibling receipt:** PR #1839
+(`docs/audit/r3-evaluator-pr-1500-1803-debt-sweep.md`) merged on
+2026-05-06 as the sibling #1500-#1803 receipt.
+
+## Live Residuals From #1838
+
+These items remain live after the merged #1275-#1500 receipt:
+
+- **G1.a static lens fold/report production:** `docs/briefs/r3-pr-e6-g1a-static-lens-fold-dispatch-packet.md`
+  is the static top-level `Lens<C>` fold/report slice. The live pressure is
+  report production through declared substrate values, not a host-side mirror.
+- **G1.b generic dispatch:** generic `fold_lens<C>` remains held on X1.b
+  S1/S3. The relevant boundary is in `docs/briefs/x1b-evaluator-impact-audit.md`
+  and the G1.a dispatch packet: no parameter-headed runtime callee shortcut.
+- **Descent proof consumer:** `LoopBound::Descent` stays a fail-closed
+  evaluator residual. `docs/briefs/r3-pr-e5-loop-readiness-audit.md` keeps
+  Descent outside cardinality-loop execution until a Substrate termination
+  proof carrier exists and the evaluator consumes it.
+- **SymbolicCost runner predicate:** `SymbolicCostExprEquals` is outside the
+  body evaluator. It belongs to ROADMAP Pattern B / runner predicate authority
+  and `docs/briefs/r2-evaluator-test-runner-authority-ratchet.md`, not to
+  `src/v3/compiler/src/lib.rs` body-evaluator closure.
+
+## Next Audit Queue
+
+The next queue should not reopen #1275-#1500 or #1500-#1803. It should
+consume #1838 plus merged sibling #1839 and then sweep the
+**post-#1803 evaluator authority surface**.
+
+**Queue name:** R3 Evaluator post-#1803 authority sweep.
+
+**Primary range:** merged PRs **#1804 onward** that touch evaluator-owned
+or evaluator-consuming surfaces:
+
+- `src/v3/compiler/src/lib.rs` evaluator functions and runtime `Value`;
+- `src/v3/compiler/src/lens_apply.rs` only when it is cited as an evaluator
+  compatibility seam, not as generic fold authority;
+- `src/v3/compiler/src/test_runner.rs` predicate/producer arms;
+- evaluator dispatch/readiness docs under `docs/briefs/`;
+- evaluator audit receipts under `docs/audit/`;
+- ROADMAP Pattern B / Pattern C rows when they name evaluator or runner
+  predicate authority.
+
+**Trigger to fire the queue:** start this sweep when both of these are true:
+
+1. The merged #1839 receipt is available to the Phase 4 compile.
+2. The next evaluator implementation/audit PR after #1803 lands or receives
+   blocking review that changes one of the live residuals above.
+
+If no implementation PR fires the second condition, the Director / Evaluator
+Manager can still fire the queue manually for the next R3 debt-sweep compile
+pass.
+
+## STOP Conditions
+
+Stop and route back to the Evaluator Manager instead of landing a local
+classification if the sweep finds any of these:
+
+- **Callable state contradiction:** live `eval_transform_node` behavior and
+  evaluator dispatch/readiness docs disagree on whether a callable surface is
+  executable, retired, or still fail-closed. Record the conflict; do not choose
+  one authority locally.
+- **G1.a/G1.b boundary blur:** any PR claims generic `fold_lens<C>` behavior
+  while X1.b S1/S3 is still held, or uses host Rust to bypass runtime-callee
+  dispatch.
+- **Descent without proof carrier:** any evaluator consumer treats
+  `LoopBound::Descent` as executable without a named Substrate termination
+  proof carrier and fail-closed residual taxonomy.
+- **Runner predicate expansion:** any new `test_runner.rs` predicate/producer
+  arm lands without a dissolution hook into evaluator/PB-runtime authority or
+  without a Pattern B row.
+- **New runtime mirror:** any new host-side `Value`, report, witness, lens, or
+  dimension carrier appears without a same-PR bridge class and dissolution
+  trigger.
+- **Unverifiable PR-range claim:** any receipt cites off-branch PR comments,
+  issue comments, or stale line numbers as sole authority for a live state.
+  Replace with in-repo files, PR metadata, or STOP.
+
+## Phase 4 Compile Handoff
+
+The Phase 4 compile should combine:
+
+- #1838 / `docs/audit/r3-evaluator-pr-1275-1500-debt-sweep.md` for the
+  #1275-#1500 slice;
+- #1839 / `docs/audit/r3-evaluator-pr-1500-1803-debt-sweep.md` for the
+  #1500-#1803 slice;
+- this packet's post-#1803 queue definition.
+
+Do not infer global debt counts from this packet. Its job is to preserve the
+next evaluator audit boundary and STOP criteria so the broader
+`docs/audit/r3-debt-sweep-2026-05-06.md` compile can consume evaluator evidence
+without silently closing live residuals.