bible: embed only the Vulgate by default; other corpora opt-in

Split the bundled corpora so the default binary carries only the
public-domain Latin Vulgate. wuj/drb/grb move to corpora_optional/ and are
compiled in only with `-tags fullbible`, or dropped into the user corpora
dir at runtime. This keeps the distributed AGPL binary free of third-party
scripture text -- bible corpora are not covered by lectio's licence.

- bible: read corpus files/metadata from core + optional embed FS
  (embReadCorpus/embCorpusFiles); optionalFS is set only under the tag.
- config: default `versions` now reflects corpora actually available in the
  build (Vulgate first), so a vul-only binary offers no absent versions.
- Makefile: `make build` = vul only; `make build-full` embeds the rest;
  `make test` runs with -tags fullbible; check-corpora validates both dirs.
- tests: corpusmeta asserts on vul (the always-embedded corpus); the
  versions-default expectation follows availableVersions().

1 files changed, 4 insertions, 1 deletions

diff --git a/internal/config/config_test.go b/internal/config/config_test.go
index 14823b8..1035426 100644
--- a/internal/config/config_test.go
+++ b/internal/config/config_test.go
@@ -16,7 +16,10 @@ func TestLoadSeeds(t *testing.T) {
 	if cfg.DefaultVersion != "vul" || cfg.Offline {
 		t.Errorf("defaults wrong: %+v", cfg)
 	}
-	wantVersions := []string{"wuj", "vul", "grb", "drb"}
+	// Versions defaults to the corpora actually available in this build, Vulgate
+	// first then the rest sorted. Tests build with -tags fullbible, so all four
+	// are present (see Makefile); a default vul-only binary would list just vul.
+	wantVersions := []string{"vul", "drb", "grb", "wuj"}
 	if len(cfg.Versions) != len(wantVersions) {
 		t.Errorf("versions default = %v, want %v", cfg.Versions, wantVersions)
 	} else {