feat!: promote bible, local, and scrape to importable packages

Move the engine and both adapters out of internal/ so the project is
usable as a library: import github.com/davidgrldo/alkitab-api/{bible,
local,scrape}. The HTTP server stays internal — it is the app, not the
API. Adds package docs and a README "Use as a library" section with a
verified example.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: davidgrldo

README.md

@@ -66,6 +66,40 @@ docker build -t alkitab-api . && docker run -p 3000:3000 alkitab-api
 `GET /healthz` answers `ok` for liveness probes; the server shuts down
 gracefully on SIGINT/SIGTERM.
 
+## Use as a library
+
+The engine and adapters are importable — the HTTP server is just one consumer:
+
+```bash
+go get github.com/davidgrldo/alkitab-api
+```
+
+```go
+package main
+
+import (
+	"fmt"
+
+	"github.com/davidgrldo/alkitab-api/bible"
+	"github.com/davidgrldo/alkitab-api/local"
+)
+
+func main() {
+	src, err := local.New("") // "" = embedded public-domain sample; or your ALKITAB_DATA_DIR
+	if err != nil {
+		panic(err)
+	}
+	eng := bible.New(src)
+
+	ch, _ := eng.Chapter("kjv", "3john", 1)
+	fmt.Println(ch.Verses[3].Content) // I have no greater joy…
+}
+```
+
+Compose sources with `bible.NewChain(local, scrape)` — the engine checks the
+`bible.Corpus` capability by type assertion, so search/daily/random work
+exactly when the active source can support them.
+
 ## Endpoints
 
 | Method | Path | Description |

internal/bible/chain_integration_test.go bible/chain_integration_test.gointernal/bible/chain_integration_test.go renamed to bible/chain_integration_test.go

@@ -3,8 +3,8 @@ package bible_test
 import (
 	"testing"
 
-	"github.com/davidgrldo/alkitab-api/internal/bible"
-	"github.com/davidgrldo/alkitab-api/internal/local"
+	"github.com/davidgrldo/alkitab-api/bible"
+	"github.com/davidgrldo/alkitab-api/local"
 )
 
 // fakeScrape is a minimal bible.Source standing in for the scrape adapter.

internal/bible/engine.go bible/engine.gointernal/bible/engine.go renamed to bible/engine.go

@@ -1,3 +1,7 @@
+// Package bible is the core of alkitab-api: domain types, the Source and
+// Corpus contracts, a caching Engine, and a fallback Chain for composing
+// sources. Pair it with an adapter such as local (embedded/BYOD JSON) or
+// scrape (runtime proxy) — dependencies always point inward.
 package bible
 
 import "errors"

internal/bible/engine_test.go bible/engine_test.gointernal/bible/engine_test.go renamed to bible/engine_test.go

@@ -11,9 +11,9 @@ import (
 	"syscall"
 	"time"
 
-	"github.com/davidgrldo/alkitab-api/internal/bible"
-	"github.com/davidgrldo/alkitab-api/internal/local"
-	"github.com/davidgrldo/alkitab-api/internal/scrape"
+	"github.com/davidgrldo/alkitab-api/bible"
+	"github.com/davidgrldo/alkitab-api/local"
+	"github.com/davidgrldo/alkitab-api/scrape"
 	"github.com/davidgrldo/alkitab-api/internal/server"
 )
 

internal/bible/metadata.go bible/metadata.gointernal/bible/metadata.go renamed to bible/metadata.go

@@ -9,7 +9,7 @@ import (
 	"strings"
 	"time"
 
-	"github.com/davidgrldo/alkitab-api/internal/bible"
+	"github.com/davidgrldo/alkitab-api/bible"
 )
 
 type Server struct {