Add Dirshu Daf HaYomi B'Halacha daily learning schedule

.gitignore

@@ -132,3 +132,5 @@ dist
 .yarn/build-state.yml
 .yarn/install-state.gz
 .pnp.*
+
+__pycache__/

CLAUDE.md

@@ -0,0 +1,91 @@
+# CLAUDE.md — working notes for `@hebcal/learning`
+
+Daily Jewish learning schedules (Daf Yomi, Mishna Yomi, Rambam, 929, …),
+published as a plugin for the `DailyLearning` registry in `@hebcal/core`.
+`README.md` is the user-facing list of schedules; this file is for working in
+the repo.
+
+Long-form notes for one schedule live in **`dirshuDafHalacha.md`** — Dirshu's
+Daf HaYomi B'Halacha is the only calendar here that is a finite transcribed
+table rather than a perpetual cycle, and it has a lot of provenance behind it.
+Read that file before touching `src/dirshuDafHalacha*` or `tools/dirshu-luach/`.
+
+---
+
+## Layout
+
+```
+src/       <name>Base.ts  pure calculation, exports the lookup function
+           <Name>Event.ts hebcal Event subclass: render / renderBrief / url
+           <name>.ts      side-effect module: DailyLearning.addCalendar(...)
+           <name>.json    lookup table, where the cycle needs one
+           common.ts      getAbsDate, checkTooEarly, formatBeginEndRange,
+                          gematriyaNN, sefariaUrl, the LearningDate type
+           index.ts       public exports (+ imports register.js)
+           register.ts    side-effect imports of every <name>.ts
+           locale.ts      wires po/*.po into Locale
+po/        he.po, ashkenazi.po
+test/      vitest specs, one per schedule plus cross-cutting suites
+tools/     one-off extraction pipelines (currently only dirshu-luach)
+```
+
+Every schedule follows the same three-module split. `*Base.ts` knows nothing
+about hebcal `Event`s and can be imported on its own (README documents these as
+the "low-level APIs"); `*Event.ts` renders; `<name>.ts` registers.
+
+## Adding or changing a schedule
+
+1. `src/<name>Base.ts` — the calculation. Take a `LearningDate` (an `HDate`, a
+   `Date`, or an R.D. number), normalise with `getAbsDate`, guard the start
+   with `checkTooEarly`, and export the start date as `<name>Start`.
+2. `src/<Name>Event.ts` — extend `DailyLearningEvent`. Override `category`,
+   `render`, `renderBrief`, `url` and `getCategories`. Use
+   `Locale.isHebrewLocale(locale)` to branch on Hebrew, `gematriyaNN` for
+   Hebrew numerals, `sefariaUrl` to build links.
+3. `src/<name>.ts` — `DailyLearning.addCalendar('<name>', hd => …)`. **Return
+   `null` when there is no learning that day**; that is the registry's
+   contract. Throw `RangeError` only for dates before the cycle began.
+4. Wire it into **both** `src/index.ts` (exports) and `src/register.ts`
+   (side-effect import). A schedule missing from `register.ts` silently fails
+   to appear in `import '@hebcal/learning'`.
+5. Add translations to `po/he.po` and `po/ashkenazi.po` for any new
+   user-visible string.
+6. Add `test/<name>.spec.ts` and a line to `README.md`.
+
+## Conventions
+
+- **R.D. day numbers** are the internal currency. `abs % 7 === 0` is a Sunday.
+  Prefer closed-form arithmetic on the R.D. number to walking forward from the
+  epoch: `test/cycleRollover.spec.ts` exists because three calendars used to
+  walk, and both grew without bound for far-future dates and drifted.
+- **`test/calendarDifferential.spec.ts`** folds every day of the supported
+  range into a checksum generated from the pre-optimisation implementation. If
+  you change cycle math and it fails, you changed output for at least one day
+  in ~200 years — find out which before updating the constant.
+- **Generated files are gitignored — never commit them.** `npm run build`
+  writes `src/*.json.ts` (from `src/*.json`) and `src/*.po.ts` (from `po/*.po`);
+  TypeScript imports the `.json.ts` form, so a new `src/<name>.json` needs no
+  build-script change but does need a build before `tsc` will resolve it.
+- `npm test` runs `pretest` → `build` (`po2json` + `build:json2js` + `tsc`)
+  first, so a type error fails the test run.
+- **Formatting**: `npm run format` (prettier) and `npm run lint` (oxlint), or
+  `npm run fix` for both. `*.json`, `*.yml`, `*.md` and `test/*` are in
+  `.prettierignore` — do not reformat them. Prettier will happily reformat
+  files that were already unformatted on `main`; check `git diff --stat` before
+  committing and revert unrelated churn.
+- **CI** (`.github/workflows/node.js.yml`) runs `npm ci && npm run build && npm
+  test` on Node 22, 24 and 26.
+
+## Two kinds of schedule
+
+Most calendars here are **perpetual**: a start date plus arithmetic, optionally
+with a fixed table for one cycle's worth of content (`bavli.json`,
+`mishnayot.json`, `arukhHaShulchanYomi.json`, `kitzurSa.json`). They answer for
+any date from their start onward.
+
+`dirshuDafHalacha` is the exception: a **bounded table** with a data horizon,
+which returns `null` past the end. Both the timing rule and the cycle boundary
+are known, but the cycles do not repeat exactly, so it cannot be closed with a
+modulo. The evidence is in the file header of `src/dirshuDafHalachaBase.ts`;
+the full story, the sources and the extraction pipeline are in
+`dirshuDafHalacha.md`.

README.md

@@ -58,6 +58,15 @@ Daily study of the Arukh HaShulchan Yomi, a work of halacha written by Yechiel M
 Summary of the Shulchan Aruch of Rabbi Yosef Karo,
 authored by Rabbi Shlomo Ganzfried in 1864.
 
+#### Daf HaYomi B'Halacha (Dirshu) - `dirshuDafHalacha`
+Dirshu's daily Mishnah Berurah program. One amud of the Dirshu edition is
+covered on each of Sunday through Thursday (Yom Tov included — the schedule
+never skips a weekday), and Friday and Shabbat review (chazarah) that week's
+five days. Readings are given as Shulchan Arukh, Orach Chayim `siman:seif`
+references, transcribed from Dirshu's luach booklets, Hebrew pocket luachs and
+wall calendars. They run from the third cycle's first day, 20 February 2022,
+through 31 August 2027
+
 ### Ethics
 
 #### Sefer Chofetz Chaim - `chofetzChaim`