fix(s3-followup): enforce V5 rule 4 + mark H3/H4/H5/V5/V6 done

serialization.hpp: `found_dofvector` was set but never checked after
the parse loop, leaving rule 4 of the strict-subset (§doc line 285)
unenforced.  Add the missing post-loop throw so a ConformalResult XML
that omits the <DOFVector> element is rejected with a clear error
instead of silently returning an empty x.  Update the docstring to
remove the misleading "silently returns" note.

finding-orchestration.md: mark H3/H4/H5/V5/V6 ✅ and record the S3
session as complete.  Implementation landed in commit 135bcf0 (P1
merge bd613a6); PR #45 code commits were redundant — the only net-new
change in this follow-up is the V5 enforcement fix + tracker update.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

code/include/serialization.hpp

@@ -283,8 +283,8 @@ inline void save_result_xml(
 ///  3. A line containing `<DOFVector` must carry the `>` character (tag
 ///     open) on the same line.
 ///  4. The `<DOFVector` element must be present and must produce a
-///     non-empty doubles list (a missing DOFVector silently returns an
-///     empty x, which is incorrect for any mesh with at least one DOF).
+///     non-empty doubles list (a missing DOFVector element causes a
+///     `std::runtime_error` — enforced after the parse loop).
 inline std::vector<double> load_result_xml(
     const std::string& path,
     NewtonResult*       res      = nullptr,
@@ -386,6 +386,13 @@ inline std::vector<double> load_result_xml(
                 " Only the format written by save_result_xml is supported.");
     }
 
+    // V5 rule 4: <DOFVector> must be present in every well-formed ConformalResult.
+    if (found_root && !found_dofvector)
+        throw std::runtime_error(
+            "conformallab: XML strict-subset violation in " + path
+            + ": <DOFVector> element not found. Only the format written by"
+            " save_result_xml is supported.");
+
     return x;
 }
 

doc/reviewer/finding-orchestration.md

@@ -70,10 +70,10 @@ Status: ✅ done · ⬜ open (actionable) · ⏸ deferred (intentional) · ⛔ b
 | I1 | test-cov | 🟡 | ✅ | Opus | S2 |
 | H1 | test-cov | 🔵 | ✅ | Opus | S2 |
 | N7 | numerics | 🔵 | ✅ | Opus | S2 |
-| **H3** | test-cov | 🔵 | ⬜ | Sonnet→🔍Opus | **S3** |
-| **H4** | test-cov | 🔵 | ⬜ | Sonnet→🔍Opus | **S3** |
-| **H5** | test-cov | 🔵 | ⬜ | Sonnet→🔍Opus | **S3** |
-| **V5, V6** | input-val | 🔵 | ⬜ | Sonnet→🔍Opus | **S3** |
+| **H3** | test-cov | 🔵 | ✅ | Sonnet→🔍Opus | **S3** |
+| **H4** | test-cov | 🔵 | ✅ | Sonnet→🔍Opus | **S3** |
+| **H5** | test-cov | 🔵 | ✅ | Sonnet→🔍Opus | **S3** |
+| **V5, V6** | input-val | 🔵 | ✅ | Sonnet→🔍Opus | **S3** |
 | **N2** | numerics | 🟡 | ⬜ | Haiku→🔍Opus | **S4** |
 | **thread-safety doc** | thread-safety | 🟡 | ⬜ | Haiku→🔍Opus | **S4** |
 | **M3** | math-cite | 🟡 | ⬜ | Haiku→🔍Opus | **S4** |
@@ -126,14 +126,18 @@ CGAL result types (`Conformal_map_result`, `Hyper_ideal_map_result`,
 
 </details>
 
-### ⬜ S3 — Robustness & test-gap closure (Sonnet → 🔍 Opus)
-- **H3** — `enforce_gauss_bonnet` reports the magnitude of the applied correction.
-- **H4** — test `reduce_to_fundamental_domain` boundary `Im(τ)==0.0`.
-- **H5** — integration test for the degenerate-triangle path in the Newton solve.
-- **V5** — make the hand-rolled XML reader *reject* reformatted-but-valid XML
-  instead of silently mis-reading it into zeros.
-- **V6** — DOF-vector-vs-mesh size check on load.
-- **🔍 Opus review:** verify the new rejections don't break valid round-trips.
+### ✅ S3 — Robustness & test-gap closure (DONE, 2026-06-01, Sonnet impl + Opus review)
+Implementation shipped in commit `135bcf0` (included in P1 merge `bd613a6`).
+Follow-up commit closes the doc-tracker gap and fixes dead `found_dofvector` variable
+(V5 rule 4: `<DOFVector>` missing now throws instead of silently returning empty `x`).
+- **H3** — `enforce_gauss_bonnet` returns `|deficit|` (both overloads); 3 new tests.
+- **H4** — `ReduceToFD_ThrowsForRealAxisBoundary` covers `Im(τ)==0.0` exact boundary.
+- **H5** — 2 integration tests: sliver triangle (no crash/NaN) + exact-degenerate collinear.
+- **V5** — `load_result_xml` rejects non-conforming XML (3 strict-subset checks); canonical
+  round-trip regression test passes. V5 rule 4 (`<DOFVector>` must be present) now enforced.
+- **V6** — `check_dof_vector_size(x, expected, context)` throws on mismatch; 3 new tests.
+- **🔍 Opus review:** CHANGES-REQUESTED resolved — implementation correct; code commits
+  were redundant with `135bcf0` on main; doc follow-up applied on `chore/s3-followup`.
 
 ### ⬜ S4 — Documentation & citations (Haiku → 🔍 Opus)
 - **N2** — `doc/math/tolerances.md`: every numerical threshold, its role, and