feat(config): reading_lang/reading_version + ReadingCorpus resolver

Task 3 of national-bibles. Adds reading_lang (any language code) and
reading_version (explicit corpus code) config fields, setField cases,
renderConfigINI lines + self-documenting header, and Config.ReadingCorpus():
reading_version > reading_lang match > ui_language match > "" (Latin fallback
applied by the caller).

Also adds an `autoselect` corpus-metadata flag (default true), surfaced during
this task: the built-in wuj declares lang=pl, so lang-auto would have
re-selected the incomplete Wujek for Polish users and defeated the wuj-drop.
wuj.ini now sets autoselect=false, so it is reachable only via an explicit
reading_version or --ref; the resolver's language auto-match skips
non-autoselectable corpora. A corrected Wujek drop-in (autoselect defaults
true) auto-serves Polish with zero config.

5 files changed, 63 insertions, 2 deletions

diff --git a/internal/bible/corpora/wuj.ini b/internal/bible/corpora/wuj.ini
index 8364923..22eeca3 100644
--- a/internal/bible/corpora/wuj.ini
+++ b/internal/bible/corpora/wuj.ini
@@ -2,3 +2,4 @@
 lang = pl
 name = Wujek (Polish)
 psalm_system = vulgate
+autoselect = false
diff --git a/internal/bible/corpusmeta.go b/internal/bible/corpusmeta.go
index 04b9dcb..60d90a9 100644
--- a/internal/bible/corpusmeta.go
+++ b/internal/bible/corpusmeta.go
@@ -3,15 +3,20 @@ package bible
 import "github.com/lukaszkasprzak/lectio/internal/ini"
 
 // CorpusMeta is the sidecar metadata for a bible corpus (<code>.ini).
+// Autoselect (default true) governs whether the corpus may be picked by the
+// reading resolver's language auto-match; a corpus with Autoselect=false stays
+// reachable only via an explicit reading_version or --ref (e.g. the built-in
+// wuj, which is incomplete). See docs national-bibles design.
 type CorpusMeta struct {
 	Code, Lang, Name, PsalmSystem, Sigla string
+	Autoselect                           bool
 }
 
 // parseCorpusMeta reads a section-less sidecar. ini.Parse returns
 // []ini.Section{Name, Pairs}; keys before any [section] land in the section
 // whose Name == "" (verified against internal/ini).
 func parseCorpusMeta(code string, data []byte) CorpusMeta {
-	m := CorpusMeta{Code: code}
+	m := CorpusMeta{Code: code, Autoselect: true} // absent autoselect => true
 	secs, err := ini.Parse(data)
 	if err != nil {
 		return m
@@ -30,6 +35,8 @@ func parseCorpusMeta(code string, data []byte) CorpusMeta {
 				m.PsalmSystem = p.Val
 			case "sigla":
 				m.Sigla = p.Val
+			case "autoselect":
+				m.Autoselect = p.Val != "false"
 			}
 		}
 	}
diff --git a/internal/bible/registry.go b/internal/bible/registry.go
index 2ab721b..28571ea 100644
--- a/internal/bible/registry.go
+++ b/internal/bible/registry.go
@@ -52,7 +52,7 @@ func buildRegistry() {
 			if code, ok := strings.CutSuffix(name, ".tsv"); ok {
 				regUserTSV[code] = filepath.Join(userDir, name)
 				if _, have := regMeta[code]; !have {
-					regMeta[code] = CorpusMeta{Code: code, PsalmSystem: "vulgate"}
+					regMeta[code] = CorpusMeta{Code: code, PsalmSystem: "vulgate", Autoselect: true}
 				}
 			}
 		}
diff --git a/internal/config/config.go b/internal/config/config.go
index 55abd72..91fd8c3 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -18,6 +18,7 @@ import (
 
 	"github.com/pelletier/go-toml/v2"
 
+	"github.com/lukaszkasprzak/lectio/internal/bible"
 	"github.com/lukaszkasprzak/lectio/internal/calendar"
 	"github.com/lukaszkasprzak/lectio/internal/ini"
 )
@@ -38,6 +39,8 @@ const configHeader = `# lectio configuration (INI). Full-line comments only (# o
 #   all               true | false             (all readings, or just the gospel)
 #   offline           true | false             (never fetch; cache/sigla only)
 #   ui_language       en | pl                  (interface chrome; readings stay source-language)
+#   reading_lang      language for offline reading text (e.g. en, pl); blank follows ui_language
+#   reading_version   force a specific bible corpus code (e.g. drb, wuj); blank = auto-resolve
 #   sigla_style       auto | polish | english | latin  (citation dialect; auto follows ui_language)
 #   web_theme         a theme name (see docs/THEMES.md)
 #   web_port          integer; 0 = try 1099, then any free port
@@ -156,6 +159,8 @@ type Config struct {
 	All             bool                       `toml:"all"`
 	Offline         bool                       `toml:"offline"`
 	UILanguage      string                     `toml:"ui_language"`
+	ReadingLang     string                     `toml:"reading_lang"`
+	ReadingVersion  string                     `toml:"reading_version"`
 	SiglaStyle      string                     `toml:"sigla_style"`
 	WebTheme        string                     `toml:"web_theme"`
 	WebPort         int                        `toml:"web_port"`
@@ -204,6 +209,28 @@ func (c Config) SiglaLang() string {
 	}
 }
 
+// ReadingCorpus resolves which bible corpus renders offline reading text:
+// an explicit reading_version, else the first corpus matching reading_lang,
+// else the first matching ui_language, else "" (caller uses the Latin vul).
+func (c Config) ReadingCorpus() string {
+	if c.ReadingVersion != "" {
+		if _, ok := bible.Meta(c.ReadingVersion); ok {
+			return c.ReadingVersion
+		}
+	}
+	for _, lang := range []string{c.ReadingLang, NormalizeUILanguage(c.UILanguage)} {
+		if lang == "" {
+			continue
+		}
+		for _, m := range bible.CorporaForLang(lang) {
+			if m.Autoselect { // skip explicit-only corpora (e.g. the incomplete wuj)
+				return m.Code
+			}
+		}
+	}
+	return ""
+}
+
 // Selection maps the config onto the calendar engine's Selection: the form
 // (from Lectionary: "new" -> OF, "traditional" -> EF) plus the national
 // placement options, each falling back to the Universal Roman default.
@@ -507,6 +534,10 @@ func applyScalar(cfg *Config, key, val string) {
 		cfg.Offline = val == "true"
 	case "ui_language":
 		cfg.UILanguage = val
+	case "reading_lang":
+		cfg.ReadingLang = val
+	case "reading_version":
+		cfg.ReadingVersion = val
 	case "sigla_style":
 		cfg.SiglaStyle = val
 	case "web_theme":
@@ -589,6 +620,8 @@ func renderConfigINI(cfg Config) []byte {
 	fmt.Fprintf(&b, "all = %t\n", cfg.All)
 	fmt.Fprintf(&b, "offline = %t\n", cfg.Offline)
 	fmt.Fprintf(&b, "ui_language = %s\n", cfg.UILanguage)
+	fmt.Fprintf(&b, "reading_lang = %s\n", cfg.ReadingLang)
+	fmt.Fprintf(&b, "reading_version = %s\n", cfg.ReadingVersion)
 	fmt.Fprintf(&b, "sigla_style = %s\n", cfg.SiglaStyle)
 	fmt.Fprintf(&b, "web_theme = %s\n", cfg.WebTheme)
 	fmt.Fprintf(&b, "web_port = %d\n", cfg.WebPort)
diff --git a/internal/config/config_test.go b/internal/config/config_test.go
index e3af475..3830cb6 100644
--- a/internal/config/config_test.go
+++ b/internal/config/config_test.go
@@ -301,3 +301,23 @@ func TestPartShown(t *testing.T) {
 		t.Error("ewangelia not mentioned should still be shown")
 	}
 }
+
+func TestReadingCorpusResolution(t *testing.T) {
+	// drb is an embedded corpus with lang=en.
+	c := Config{ReadingVersion: "drb"}
+	if got := c.ReadingCorpus(); got != "drb" {
+		t.Fatalf("explicit reading_version: got %q", got)
+	}
+	c = Config{ReadingLang: "en"}
+	if got := c.ReadingCorpus(); got != "drb" {
+		t.Fatalf("reading_lang match: got %q", got)
+	}
+	c = Config{UILanguage: "en"}
+	if got := c.ReadingCorpus(); got != "drb" {
+		t.Fatalf("ui_language fallback: got %q", got)
+	}
+	c = Config{UILanguage: "pl"} // no pl corpus embedded
+	if got := c.ReadingCorpus(); got != "" {
+		t.Fatalf("no match should be empty: got %q", got)
+	}
+}