temporal(ef): Holy Name of Jesus, RG 17(a) -- fallback + Lord subject

RG 17(a): "festum Ss.mi Nominis Iesu, celebrandum dominica quae occurrit
a die 2 ad 5 ianuarii (secus die 2 ianuarii)" -- both photographic scans,
confirmed on the calendarium's own January table and the Mass propers'
own heading. Two defects closed together, since they interact through
RG 91 entry 14/RG 16(a):

1. The Sunday shape (2-5 January) now tags subject = Lord, matching
   RG 91 entry 14 ("Festa Domini II classis") -- previously subject =
   Temporal, the same defect shape Holy Family had before it.
2. The fallback (RG 17(a)'s own "secus die 2 ianuarii", the calendarium's
   "vel, ea deficiente, die 2 ianuarii") is now built: 2 January carries
   the feast whenever no Sunday falls 2-5 January that year. Before this
   fix colitur emitted no Holy Name office at all in such a year -- a
   real II-class feast simply missing, on 3,619 of 8,417 years in the
   domain (43%; 20 of the 46 years 2005-2050, independently re-derived
   against `date -d`).

Both shapes band identically at RG 91 entry 14's MOVABLE half
(Precedence_ef.entry_14_movable_band) -- one feast, not two differently
classified ones, per the Mass propers' own single heading covering both
dates. No live collision exists in the current sanctoral data (nothing
fixed-date falls 2-5 January besides a Commemoration_only entry on 5
Jan), so the RG 16(a)/RG 112(a) interaction is proved with synthetic
precedence-level fixtures mirroring Holy Family's own precedent, not a
live-data regression. One asymmetry the synthetic tests found and kept
honest rather than forced: a losing Holy-Name-Sunday is privileged
(RG 109(a), "of a Sunday") and survives RG 111(a)'s cap; a losing
Holy-Name-fallback is not (2 January is not a Sunday, and no other
RG 109(a)-(f) category applies to it), so it gets no commemoration at
all if ever outranked -- both individually correct readings of RG 109/111's
closed lists.

Golden pins follow the brief's own vacuity warning: the Sunday shape
already emitted the right slug/rank/colour before this fix (an ordinary
Sunday and Holy Name coincide on those fields), so its pin asserts
subject explicitly rather than pinning the whole line uncritically; the
fallback pin (2029-01-02) is the one with teeth against the larger
defect, reddening on slug/rank/subject together if reverted.

Mutation-tested: each half of the fix reverted separately reddens
exactly its own tests (Sunday subject: the dedicated unit test, the
golden pin's subject field, one precedence end-to-end test; fallback:
the fallback unit/anchor/golden tests, the new C16 differential count,
and both shapes of the precedence end-to-end tests) and nothing else.

Adds data/ef/expected-divergences.sexp's C16 (lectio has no fallback for
this window at all) -- the lectio differential's own count, independently
re-derived against `date -d` for the fixture's 2005-2050 span, not
transcribed from the domain-wide figure. The missalemeum oracle window
(2026-2027) exercises only the Sunday shape and needed no new entry:
subject is not one of its compared fields, and both years' rows already
corroborate the Sunday-shape ranking (missalemeum's own 2026-01-04 and
2027-01-03 rows: rank 2, white, title "Holy Name of Jesus").

1 files changed, 53 insertions, 0 deletions

diff --git a/test/test_golden.ml b/test/test_golden.ml
index 1724375..c5aa65a 100644
--- a/test/test_golden.ml
+++ b/test/test_golden.ml
@@ -634,6 +634,53 @@ let test_holy_family_earliest_possible_date_2024 () =
     "2024-01-07 sunday season=christmastide week=- slug=ef-time-after-epiphany-sunday-1 rank=class-2 \
      colour=white subject=lord comms=[] in=- out=[]"
 
+(* Most Holy Name of Jesus (RG 17(a), scan-verified, docs/research/rules-
+   register.md §6.2/§4): "festum Ss.mi Nominis Iesu, celebrandum dominica
+   quae occurrit a die 2 ad 5 ianuarii (secus die 2 ianuarii)" -- unlike Holy
+   Family (RG 17(b), immediately above), this window CAN be, and routinely
+   is, empty of a Sunday (3,619 of 8,417 years domain-wide) -- the
+   calendarium's own fallback, "vel, ea deficiente, die 2 ianuarii", is what
+   the SECOND pin below exercises.
+
+   *** THIS FILE'S OWN VACUITY WARNING, APPLIED DIRECTLY ***
+
+   [test_holy_name_sunday_shape_2026] pins a year where the Sunday shape
+   fires -- slug/rank/colour/season/comms here are ALL already what
+   [T.sunday_slug]'s Christmastide branch computed before this task's fix
+   (the identical accident Holy Family's own [describe] note above already
+   explains for its shape): an unnamed Sunday and Holy Name of Jesus share
+   every one of those fields on this date. Reverting the fix leaves this
+   pin GREEN except for [subject] -- the ONE field it actually tests, same
+   discipline as Holy Family's own "coordinator finding 4" fix. This pin
+   earns its place only by asserting [subject] explicitly, not by pinning
+   the whole line uncritically.
+
+   [test_holy_name_fallback_2029] is the pin that actually has teeth against
+   the LARGER of the two defects this task closed: before the fix, colitur
+   emitted NO Holy Name office at all in a fallback year -- not merely an
+   unnamed generic Sunday (Holy Family's own pre-fix shape), but the
+   ordinary Christmastide ferial slug (`ef-christmas-1-tuesday`, class-4)
+   the task brief's own example names. Reverting the fallback half of the
+   fix reddens this pin on EVERY field (slug, rank, subject), not only one --
+   the shape this file's header calls "the whole line moved", the opposite
+   of the Sunday pin's own narrow, single-field teeth. *)
+let test_holy_name_sunday_shape_2026 () =
+  check ~msg:"2026-01-04: Holy Name of Jesus, Sunday shape -- oracle-corroborated (missalemeum's own \
+              2026-01-04 row: rank 2, white, title \"Holy Name of Jesus\")"
+    2026 1 4
+    "2026-01-04 sunday season=christmastide week=- slug=ef-holy-name-sunday rank=class-2 colour=white \
+     subject=lord comms=[] in=- out=[]"
+
+let test_holy_name_fallback_2029 () =
+  check ~msg:"2029-01-02: Holy Name of Jesus, FALLBACK shape (RG 17(a)'s own \"secus die 2 ianuarii\", the \
+              calendarium's \"vel, ea deficiente, die 2 ianuarii\") -- no Sunday falls 2-5 January 2029 \
+              (`date -d 2029-01-0{2,3,4,5} +%u` = 2,3,4,5, independently confirmed), so 2 January itself \
+              carries the feast; before this task's fix colitur emitted `ef-christmas-1-tuesday class-4` \
+              here instead -- a real, II-class office simply missing, not merely misnamed"
+    2029 1 2
+    "2029-01-02 tuesday season=christmastide week=- slug=ef-holy-name rank=class-2 colour=white \
+     subject=lord comms=[] in=- out=[]"
+
 (* 2025-02-02, the other real instance of the SAME pattern -- not a
    contrasting second direction, per this task's fix round 1 (CRITICAL
    finding, item 1, reverted; see register §6.0 for the full account).
@@ -793,6 +840,12 @@ let suite =
         `Quick test_holy_family_excludes_baptism_2030;
       Alcotest.test_case "Holy Family, earliest possible date (2024-01-07)" `Quick
         test_holy_family_earliest_possible_date_2024;
+      Alcotest.test_case "Holy Name of Jesus (RG17(a)), Sunday shape, subject asserted (2026-01-04)" `Quick
+        test_holy_name_sunday_shape_2026;
+      Alcotest.test_case
+        "Holy Name of Jesus, fallback shape (RG17(a) \"secus die 2 ianuarii\", 2029-01-02 -- no Sunday in \
+         the window)"
+        `Quick test_holy_name_fallback_2029;
       Alcotest.test_case
         "ef-rebootstrap: RG91 entry24 (III-class feast) outranks entry28 (class-4 feria) -- the six dates \
          deferred since 2038's own Easter-extreme pin (2008-04-02/04/05, 2038-03-06/08/09)"