internal/app: update doc comments

A lot of these comments are quite old and have not been updated to reflect changes.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/app/app.go

@@ -1,19 +1,16 @@
-// Package app defines the generic [App] interface.
+// Package app implements high-level hakurei container behaviour.
 package app
 
 import (
-	"context"
-	"log"
 	"syscall"
 	"time"
 
 	"hakurei.app/hst"
 	"hakurei.app/internal/app/state"
-	"hakurei.app/internal/sys"
 )
 
 type App interface {
-	// ID returns a copy of [ID] held by App.
+	// ID returns a copy of [state.ID] held by App.
 	ID() state.ID
 
 	// Seal determines the outcome of config as a [SealedApp].
@@ -51,11 +48,3 @@ func (rs *RunState) SetStart() {
 	now := time.Now().UTC()
 	rs.Time = &now
 }
-
-func MustNew(ctx context.Context, os sys.State) App {
-	a, err := New(ctx, os)
-	if err != nil {
-		log.Fatalf("cannot create app: %v", err)
-	}
-	return a
-}