refactor(viewer): consolidate rendering and harden uploads

bible-local/architecture/api-surface.md

@@ -6,7 +6,8 @@ The package is intended to be embedded by other Go applications.
 
 Current package shape:
 
-- `viewer.RenderHTML(snapshot []byte) ([]byte, error)`
+- `viewer.RenderHTML(snapshot []byte, title string) ([]byte, error)`
+- `viewer.RenderHTMLWithOptions(snapshot []byte, title string, opts viewer.RenderOptions) ([]byte, error)`
 - `viewer.NewHandler(viewer.HandlerOptions{...}) http.Handler`
 - `viewer.NewStandaloneHandler(viewer.HandlerOptions{...}) http.Handler`
 
@@ -32,6 +33,10 @@ Embedded handler endpoints:
 - `GET /healthz` - basic process health
 - `GET /static/...` - embedded static assets
 
+Internal asset and form URLs are relative so the documented
+`http.StripPrefix("/chart", ...)` integration works below `/chart/` as well as
+at the server root. Snapshot request bodies are limited to 64 MiB.
+
 ## UI Route Rules
 
 - No multi-product navigation