refactor: remove the niedziela/missalemeum scrapers, bt, traditional_lang

The daily view now computes entirely offline (previous commit), so retire the
network path and everything that served it:

- Delete internal/tradlit (missalemeum) and the niedziela scraper from
  internal/liturgy (fetch/store/parse + fixtures); keep Section, DayInfo and
  ExtractCitation.
- Remove the "bt" version everywhere (render gatherBT + branches, config,
  i18n, web form, TUI) and bible.ToEnglishRef (Polish citation converter).
  A legacy config carrying "bt" migrates to "wuj" on load (config.migrateBT).
- Remove the traditional_lang config field and the -g/--lang flag from all
  three binaries.
- Drop the now-dead flags -R/--refresh, -o/--offline, -u/--update,
  -C/--clean and the harvest/clean commands.
- New defaults: versions = wuj,vul,grb,drb; default_version = vul.

Update the README (offline-by-design, no harvest/update), help text, and
stale niedziela/bt doc comments. Tests updated for the offline reality;
go test ./... and go vet ./... are clean, all three binaries build and run
offline (OF + EF, compare, web).

1 files changed, 5 insertions, 9 deletions

diff --git a/internal/web/render.go b/internal/web/render.go
index 2cbf331..3ea52e3 100644
--- a/internal/web/render.go
+++ b/internal/web/render.go
@@ -191,12 +191,9 @@ func buildColumnViews(secs []liturgy.Section, versions []string, lectionary, lan
 	return views
 }
 
-// interlinearVersions maps versions through the same bt->wuj substitution
-// render.OfflineVersions performs for offline mode: "bt" (niedziela.pl
-// paragraph text) carries no verse numbers and cannot interleave, so it is
-// dropped, substituting "wuj" (the Polish-language bible version) in its
-// place unless "wuj" was already selected. Reuses render.OfflineVersions
-// rather than duplicating its two-line transform.
+// interlinearVersions maps versions through render.OfflineVersions, which
+// substitutes a legacy "bt" with "wuj" (unless "wuj" is already selected).
+// Every remaining version is a versified corpus that interleaves cleanly.
 func interlinearVersions(versions []string) []string {
 	return render.OfflineVersions(versions)
 }
@@ -288,9 +285,8 @@ func webVersionLabel(v, lang string) string {
 	return v
 }
 
-// readerCorpusVersions are the versions the /reader offers: the four with an
-// embedded full-text corpus. "bt" (the niedziela.pl scrape) has no corpus and
-// cannot be read chapter-by-chapter.
+// readerCorpusVersions are the versions the /reader offers: the four embedded
+// full-text corpora.
 var readerCorpusVersions = []string{"wuj", "vul", "grb", "drb"}
 
 // UnionChapters returns the sorted union of chapter numbers a book has across