Add March Matins readings for SanctiM-track saints

All 6 of March's SanctiM-track saints authored. St. Benedict's own
patronal feast turns out to be the richest case in this pass so far:
its Nocturn 3 is genuinely Monastic-only content (a St. Peter Damian
sermon) absent from the Tridentine track entirely, unlike every other
saint done so far where the SanctiM file just reslices the same
Tridentine text. Also caught a case (St. Gregory the Great) where a
saint's SanctiM file carries content copied verbatim from an unrelated
feast rather than anything proper to the saint himself.

TODO.md

@@ -37,7 +37,7 @@ across every hour and content type in this app.
      saints (Tridentine/Divino Afflatu-sourced, no Monastic 1617 track) are now done — see
      "Pre-1955 saints' Matins readings" below. The larger pool of saints that *do* have a
      Monastic 1617 track (`SanctiM/`) is in progress — see "SanctiM-track saints' Matins
-     readings" below — January and February done (19/23), ~130 candidates remain (March onward).
+     readings" below — January-March done (25/29), ~124 candidates remain (April onward).
    - The bulk Vulgate (Latin) + Douay-Rheims (English) scripture import into
      `src/data/scripture/` — long-term project, explicitly deferred; Matins scripture
      citations resolve to `missing` text until it lands.
@@ -1429,7 +1429,18 @@ incipit line under `isGospel: true` despite not having the full pericope text. T
 file is left as-is (not wrong, just an earlier, less clean judgment call) — this convention
 applies going forward.
 
-**Not done in this pass**: the remaining ~130 SanctiM-track candidates (March onward) — same
+**March done (6/6 saints)**: `st-thomas-aquinas`, `st-frances-of-rome`, `forty-holy-martyrs`,
+`st-gregory-the-great` (Lectio7-9's Gospel+homily is generic Chair-of-Peter content copied
+verbatim into this file, unrelated to Gregory — same lessons as
+`chair-of-st-peter-at-rome.yml`'s own sourcing, not proper to this feast, so not authored
+here), `st-joseph`, `st-benedict` (Duplex I class patronal feast — the richest SanctiM case yet:
+Nocturn 2 sourced from `Sancti/03-21.txt`'s own vita per the usual pattern, but Nocturn 3 is
+**genuinely Monastic-only content not found in `Sancti/` at all** — a St. Peter Damian sermon
+preached specifically for Benedict's own feast; no `English/SanctiM/03-21.txt` exists in the
+reference engine, so `en` for that reading is this project's own translation, marked `draft`).
+`npm test`/`tsc --noEmit` both pass.
+
+**Not done in this pass**: the remaining ~124 SanctiM-track candidates (April onward) — same
 authoring shape, continue month by month.
 
 ### Bible-plan TSV — bulk conversion done (2026-08)