web: horizontal/vertical/interlinear display modes + web_display config

Adds a display-layout option to lectio-web alongside the existing colour
themes:

- config: WebDisplay field (toml web_display), default "horizontal",
  normalized on load via the new exported config.NormalizeDisplay
  (unknown -> "horizontal", same lenient style as the other web_* fields).
- render: extracts the citation/ToEnglishRef resolution shared by
  GatherVersion into an unexported resolveRef helper (GatherVersion's
  signature/behavior unchanged) and adds GatherVerses(version, sec,
  lectionary) returning raw bible.Verse structs plus a versified flag, for
  column/interlinear alignment.
- web/render: RenderReadings gains a display parameter. "horizontal" is
  the original stacked layout, byte-for-byte the same code path as
  before. "vertical" reuses the same per-version column data in a
  .display-vertical/.vcol grid (the CLI compare view, browser-side).
  "interlinear" maps versions through render.OfflineVersions' pl->wuj
  substitution (pl has no verse numbers), gathers GatherVerses per
  version, and interleaves them by chapter:verse into .ilverse/.illine
  blocks (ordered union of keys, first versified version's order first).
- server: adds a display <select> to the top bar wired into the existing
  #controls HTMX form; a resolveQuery(cfg, r) helper replaces the
  duplicated date/lectionary/all/versions(+now display) resolution in
  indexHandler and readingsHandler.
- fold-in from the B2 review: indexHandler now populates indexData.Lookup
  via a shared renderLookup(ref, versions) helper (also used by
  lookupHandler), so a bookmarked "/?ref=...&v=..." link shows its
  lookup result instead of an empty pane.
- base.css: layout-only rules for the two new modes (no colours; themes
  stay colour-only).

go test ./..., go vet ./..., gofmt clean; go build ./cmd/lectio-web ok.

1 files changed, 24 insertions, 0 deletions

diff --git a/internal/config/config.go b/internal/config/config.go
index 9c3c3cd..c15b5a0 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -11,6 +11,7 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"strings"
 
 	"github.com/pelletier/go-toml/v2"
 )
@@ -30,6 +31,26 @@ var validVersions = map[string]bool{
 	"drb": true,
 }
 
+// validDisplays are the lectio-web reading-pane layouts.
+var validDisplays = map[string]bool{
+	"horizontal":  true,
+	"vertical":    true,
+	"interlinear": true,
+}
+
+// NormalizeDisplay lower-cases display and falls back to "horizontal" when
+// it is not one of validDisplays -- the same lenient style as the rest of
+// lectio-web's config fields (no error, just a safe default). Exported so
+// internal/web can apply the identical normalization to an explicit
+// ?display= query override, keeping the valid set in this one place.
+func NormalizeDisplay(display string) string {
+	d := strings.ToLower(display)
+	if !validDisplays[d] {
+		return "horizontal"
+	}
+	return d
+}
+
 // Config holds lectio's user-configurable settings.
 type Config struct {
 	SchemaVersion   int                        `toml:"schema_version"`
@@ -42,6 +63,7 @@ type Config struct {
 	Offline         bool                       `toml:"offline"`
 	WebTheme        string                     `toml:"web_theme"`
 	WebPort         int                        `toml:"web_port"`
+	WebDisplay      string                     `toml:"web_display"`
 	Parts           map[string]map[string]bool `toml:"parts"`
 }
 
@@ -69,6 +91,7 @@ func Default() Config {
 		Offline:         false,
 		WebTheme:        "transfiguration",
 		WebPort:         0,
+		WebDisplay:      "horizontal",
 		Parts:           nil,
 	}
 }
@@ -134,6 +157,7 @@ func Load() (Config, error) {
 		fmt.Fprintf(os.Stderr, "lectio: warning: invalid config at %s: %v; using defaults\n", path, err)
 		return def, nil
 	}
+	cfg.WebDisplay = NormalizeDisplay(cfg.WebDisplay)
 
 	if err := validate(cfg); err != nil {
 		return Config{}, err