feat(cmd): shared buildProcessor + wire immediate web summarization

Extract the engine wiring (YouTube source, AI-router summarizer, store sink)
into buildProcessor, shared by cmdRun and cmdServe. It returns (nil, nil) — not
an error — on incomplete config, which is the queue-only fallback for serve.
engineProcessor adapts the engine to web.Processor: load the video row, run the
engine, clear the manual queue flag on a produced summary (mirrors the runner).
cmdServe wires it onto web.App.Processor; cmdRun reuses buildProcessor so the
wiring is no longer duplicated.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

cmd/tapir/main.go

@@ -22,15 +22,11 @@ import (
 	"os/signal"
 	"time"
 
-	"gitea.d-ma.be/mathias/tapir/internal/adapters/llm"
 	"gitea.d-ma.be/mathias/tapir/internal/adapters/secrets"
 	"gitea.d-ma.be/mathias/tapir/internal/adapters/store"
-	"gitea.d-ma.be/mathias/tapir/internal/adapters/summarizer"
-	"gitea.d-ma.be/mathias/tapir/internal/adapters/youtube"
 	"gitea.d-ma.be/mathias/tapir/internal/auth"
 	"gitea.d-ma.be/mathias/tapir/internal/config"
 	"gitea.d-ma.be/mathias/tapir/internal/runner"
-	"gitea.d-ma.be/mathias/tapir/internal/usecase"
 	"gitea.d-ma.be/mathias/tapir/internal/web"
 	"gitea.d-ma.be/mathias/tapir/internal/web/oidc"
 )
@@ -120,24 +116,16 @@ func cmdRun(ctx context.Context, log *slog.Logger) error {
 	}
 	defer st.Close()
 
-	secretStore := secrets.NewFileStore(cfg.SecretsFile)
-	src := youtube.New(youtube.Config{
-		ClientID:           cfg.YTClientID,
-		ClientSecret:       cfg.YTClientSecret,
-		TokenSecretRef:     cfg.YTTokenRef,
-		PreferredLanguages: []string{"en"},
-	}, secretStore)
-
-	// Local Primary only; no BYO fallback for the demo (fallback nil).
-	primary := summarizer.Endpoint{
-		Client:   llm.New(cfg.GatewayURL, cfg.GatewayKey, cfg.SummarizerModel, cfg.SummarizerTimeout),
-		Provider: "local",
-		Model:    cfg.SummarizerModel,
+	// Same wiring the web serve path uses (buildProcessor). ValidateForRun above
+	// already required the engine's inputs, so a nil here is a genuine config gap.
+	engine, err := buildProcessor(cfg, st)
+	if err != nil {
+		return err
 	}
-	sum := summarizer.New(primary, nil)
-
-	engine := usecase.NewEngine(src, sum, st)
-	r := runner.New(src, st, engine, cfg.UserID, log)
+	if engine == nil {
+		return fmt.Errorf("run: incomplete summarization config (gateway, youtube credentials, secrets file)")
+	}
+	r := runner.New(engine.Source, st, engine, cfg.UserID, log)
 
 	log.Info("starting run", "user", cfg.UserID, "model", cfg.SummarizerModel,
 		"gateway", cfg.GatewayURL, "poll_interval", cfg.PollInterval)
@@ -204,6 +192,21 @@ func cmdServe(ctx context.Context, log *slog.Logger) error {
 		log.Info("web youtube connect enabled", "redirect", cfg.YTConnectRedirectURL)
 	}
 
+	// Immediate summarization for the web "Summarize" button. When the engine can
+	// be built (gateway + YouTube credentials + secrets present), a click runs the
+	// summary now in the background; otherwise the button stays queue-only and the
+	// next `tapir run` does the work (buildProcessor returns nil — never an error).
+	engine, err := buildProcessor(cfg, st)
+	if err != nil {
+		return err
+	}
+	if engine != nil {
+		app.Processor = &engineProcessor{engine: engine, store: st}
+		log.Info("web immediate summarization enabled", "model", cfg.SummarizerModel)
+	} else {
+		log.Info("web summarization is queue-only (incomplete engine config)")
+	}
+
 	srv := &http.Server{
 		Addr:              cfg.HTTPAddr,
 		Handler:           app.Router(),