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, 28 insertions, 1 deletions

diff --git a/internal/config/config.go b/internal/config/config.go
index b6c9e0e..299c942 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -269,13 +269,40 @@ func (c Config) Selection() calendar.Selection {
 	return sel
 }
 
+// availableVersions lists the corpus codes actually present in this build (the
+// embedded Vulgate, plus any compiled in with -tags fullbible or dropped into
+// the user corpora dir), Vulgate first then the rest sorted. It keeps the
+// default version list coherent with a vul-only binary: an absent corpus is
+// never offered by default, so no spurious "(not in wuj)" appears out of the
+// box. Users may still name any code explicitly in their config.
+func availableVersions() []string {
+	var rest []string
+	haveVul := false
+	for _, m := range bible.Corpora() {
+		if m.Code == "vul" {
+			haveVul = true
+			continue
+		}
+		rest = append(rest, m.Code)
+	}
+	sort.Strings(rest)
+	out := rest
+	if haveVul {
+		out = append([]string{"vul"}, rest...)
+	}
+	if len(out) == 0 {
+		out = []string{"vul"} // safety: at least the always-embedded Vulgate
+	}
+	return out
+}
+
 // Default returns lectio's built-in configuration, used when no config file
 // is found and as the base that a partial config file overrides.
 func Default() Config {
 	return Config{
 		SchemaVersion:  1,
 		Lectionary:     "new",
-		Versions:       []string{"wuj", "vul", "grb", "drb"},
+		Versions:       availableVersions(),
 		DefaultVersion: "vul",
 		Width:          0,
 		All:            false,