Give the Matins invitatory antiphon a real weekday cycle

The plain ferial fallback was a single fixed year-round text that was
actually just Monday's own antiphon, mislabeled in its own comment as
live-verified for 2026-09-06 (a Sunday). The real Monastic 1617 source
genuinely varies this antiphon Sunday-Saturday, same shape as the Matins
hymn's own weekday cycle. Adds the six missing weekday variants and
dispatches on weekday in resolveMatinsInvitatoryText.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01W8cttEhwbN3f6hiHQHqCae

TODO.md

@@ -11,10 +11,6 @@ content in the same shape, not a design change. The dated log below is that pipe
 ## Open work, in priority order
 
 1. **Mechanism gaps**
-   - **2026-09-06 invitatory antiphon questioned** — user flagged today's (2026-09-06)
-     invitatory antiphon as suspect; needs tracing back to its source (override > octave >
-     Common > season > ferial chain in `hours/matins.ts`'s invitatory resolution) to find
-     and fix whatever underlying bug or content problem produced it. Not yet investigated.
    - **Gospel+homily pairing shouldn't carry a responsory** — user, 2026-09-06: when a Matins
      Gospel pericope is immediately followed by its own patristic homily (the paired
      `gospel`/homily rendering — see `hours/matins.ts`'s Gospel+homily-fold-in convention),
@@ -6445,3 +6441,28 @@ Albis", i.e. Low Sunday, not yet itself named beyond a generic ordinal — a sep
 still-open gap) carries a name distinct from the plain "Die N" pattern.
 
 `npm test` (2066 passed) and `tsc --noEmit` both pass.
+
+### Matins invitatory antiphon weekday cycle — closed (2026-09-06)
+
+User flagged 2026-09-06's (a plain Sunday, `post-pentecost-15`) invitatory antiphon as suspect.
+Traced it to a real content bug, not a resolution-order bug: `matins-invitatory-antiphon.yml` (the
+final ferial fallback in `resolveMatinsInvitatoryText`) held a single fixed year-round text
+("Veníte, * Exsultémus Dómino") that its own header claimed was "live-verified... 2026-09-06" —
+that was wrong. Querying the live reference engine for that exact date returns a different text
+("Adorémus Dóminum, * Qui fecit nos"), and querying a full week showed the real source
+(`Psalterium/Special/Matutinum Special.txt`'s `[Invit Trid_]` block) genuinely varies the plain
+`{Antiphona ex Psalterio secundum tempora}` invitatory antiphon Sunday-Saturday — same shape as the
+Matins hymn's own weekday cycle (`matins-hymn-ferial-tuesday.yml` etc., closed 2026-09-04). The
+fixed text turned out to be Monday's own real antiphon, silently standing in for every other
+weekday including Sunday.
+
+Fixed the same way as the hymn cycle: six new weekday-specific files
+(`matins-invitatory-antiphon-{sunday,tuesday,wednesday,thursday,friday,saturday}.yml`, full
+Latin+English pulled from the reference engine's own `Invit Trid_`/`Invit Trid` blocks, Latin and
+English respectively), `matins-invitatory-antiphon.yml` (no day suffix) still used for Monday.
+`hours/matins.ts`'s `resolveMatinsInvitatoryText` now dispatches on `day.weekday` for its final
+fallback tier, same pattern as `resolveMatinsHymn`'s `weekdayFerialHymnIds`. Two pre-existing tests
+in `tests/hours/matins.test.ts` hardcoded "Veníte" as the generic ferial default — both dates are
+actually Tuesdays, updated to expect Tuesday's own real text ("Jubilémus Deo").
+
+`npm test` (2066 passed) and `tsc --noEmit` both pass.