test(oracle): a second oracle year, 2038, closing step 4's blind spot

Register section 6.7 recorded that step 4 of the reading chain -- the
Common route -- had no external witness of any kind, and proved it by
mutation: corrupting a Common citation left both the 16801-day
differential and the 730-day oracle green. This closes that.

2038 is the only year in 2005-2050 in which two of the five
Common-routed saints are the observed office (Perpetua and Felicitas on
6 March, Frances of Rome on 9 March). 365 days were captured live, one
request per day, zero failures.

A separate fixture, not more rows on the existing one. sources.md
already records that the live endpoint has drifted from lectio's
archived 2026-2027 snapshot; merging two versions of one source behind a
single set of expectations would make any future disagreement
unattributable -- calendar or drift, no way to tell. Nothing in the 2038
comparison is checked against the older fixture, and its provenance file
says so, along with the fact that a live capture is not reproducible
byte-for-byte on demand the way a snapshot-derived one is.

338 of 365 days match. 27 differ, every one of them in a named,
already-adjudicated class, none unexplained: 13 the BVM Saturday votive
Mass (M26 shape 1), 7 colour (M21), 2 Judith (M28), 2 Christ the King's
week (M26 shape 2b), 1 Christmas multi-Mass (M27), 1 Perpetua's Common,
1 new. Each was decided in a different year, so 2038 re-confirms them
independently -- the point of a second window is not new rulings but
evidence the old ones are not artefacts of their own year.

Two findings came out of it. Perpetua and Felicitas: missalemeum serves
the Common of Virgins and calls them "Virgins and Martyrs" in its own
oration, where the Missal directs "Missa Me exspectaverunt, de Communi
non Virginum I loco" (scan1:27634-27635). Both Commons share the Introit
Ps 118:95-96, which is exactly why the calendarium qualifies its
direction, and both women were mothers. Verdict colitur; the mechanism
is located on missalemeum's side, not merely asserted. Passion Tuesday:
the Missal prints "Dan. 14, 27 et 28-42" (scan1:11106) and colitur
reproduces that two-part form where missalemeum collapses it to
27-42. Same verses; the convention is deliberate, appearing also in the
Seven Sorrows and the Common of Non-Virgins. Verdict colitur, cosmetic.

Citations are notation-normalised before comparing, as layer 3 already
does: Ecclus/Sir, Joann/John, Luc/Luke, Matth/Matt. Each pair was added
because a real row needed it, and no target contains its own source as a
substring, so the set is idempotent.

Not compared, stated rather than left to be found: commemorations and
observed-identity. That machinery is built around a date-literal
28-entry allow-list specific to 2026-2027, and re-deriving it for a
second year is its own task. 2038 compares rank, colour, Epistle, Gospel.

The extractor's day count was hardcoded to 730, which silently forbade
any other window. It is now a parameter defaulting to 730, so the
existing documented command keeps its guard and a partial fetch still
fails loudly instead of producing a short fixture that passes a
comparison it never ran.

Teeth, by re-running section 6.7's own experiment: corrupting the Common
of Non-Virgins II now reddens four tests, two of them external-oracle,
where the same mutation previously reddened neither oracle layer.

Residual: isidore-of-seville is still unwitnessed and needs 2035 or
2046; gregory-the-great and patrick are never the observed office in any
year 2005-2050, so no fixture in that range can reach them.

Register section 6.8 and 6.9.

1 files changed, 13 insertions, 4 deletions

diff --git a/tools/extract_missalemeum_oracle.py b/tools/extract_missalemeum_oracle.py
index 1abc574..6d3f8f0 100644
--- a/tools/extract_missalemeum_oracle.py
+++ b/tools/extract_missalemeum_oracle.py
@@ -111,10 +111,19 @@ def extract_citation(sections, section_id, date, label):
 
 
 def main():
-    if len(sys.argv) != 3:
-        print(f"usage: {sys.argv[0]} <snapshot-dir> <out-file>", file=sys.stderr)
+    # <expected-days> (added 2026-08-17, the 2038 oracle extension) is the
+    # number of day-files this run MUST produce, stated by the caller rather
+    # than hardcoded. It used to be a bare `!= 730`, which silently forbade
+    # extracting any window other than the original 2026-2027 pair. It stays
+    # MANDATORY-in-effect via its default so the existing documented command
+    # keeps its own guard unchanged: a partial fetch (a dropped HTTP request,
+    # an interrupted unpack) must fail loudly here rather than quietly
+    # produce a short fixture that then "passes" a comparison it never ran.
+    if len(sys.argv) not in (3, 4):
+        print(f"usage: {sys.argv[0]} <snapshot-dir> <out-file> [expected-days]", file=sys.stderr)
         return 2
     snapshot_dir, out_path = sys.argv[1], sys.argv[2]
+    expected_days = int(sys.argv[3]) if len(sys.argv) == 4 else 730
     src = os.path.join(snapshot_dir, "missalemeum", "en")
     rows = []
     for fname in sorted(os.listdir(src)):
@@ -153,8 +162,8 @@ def main():
             f"|{cit_first}|{cit_gospel}"
         )
 
-    if len(rows) != 730:
-        print(f"ERROR: expected 730 days, got {len(rows)}", file=sys.stderr)
+    if len(rows) != expected_days:
+        print(f"ERROR: expected {expected_days} days, got {len(rows)}", file=sys.stderr)
         return 1
 
     with open(out_path, "w", encoding="utf-8") as f: