feat(shell): yellow active session, growing composer, phase title, refined activity log, arrow panel toggle

Fix six GUI defects, verified live against the real stack:

- NavSessions: mark the in-progress (active) session in yellow (warning
  token) — both its status dot and its row background.
- SteerInput: the composer is now an auto-growing textarea that wraps and
  grows vertically (caps at 160px, then scrolls); Enter sends, Shift+Enter
  inserts a newline.
- WorkflowBar: show a synthetic title of the current phase under the 8 dots
  from static EN/IT strings (no LLM); English is displayed to match the chrome.
- CentralStatus: reformat the 5-line system-message tail as a structured,
  monospace list with per-line markers and an emphasized last line.
- AppShell + CentralStatus: move the left Model-activity panel toggle off the
  working spinner (now a pure status indicator) onto a dedicated arrow button
  (→ opens, ← closes).
- gate: rename the phase-confirm button "Conferma e prosegui" → "Salva e
  procedi" (builders.js + its L1 test).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/shell/WorkflowBar.tsx

@@ -13,6 +13,21 @@ const PHASES = [
   { id: "F8", name: "Results" },
 ];
 
+// Synthetic, human-readable title for the current phase, shown under the dots.
+// Static bilingual strings (no LLM): PHASE_LANG picks which set is displayed.
+// The rest of the app chrome is English, so the label follows suit.
+const PHASE_LANG: "en" | "it" = "en";
+const PHASE_TITLES: Record<string, { en: string; it: string }> = {
+  F1: { en: "Clarifying the question", it: "Chiarimento della domanda" },
+  F2: { en: "Linking the schema", it: "Collegamento dello schema" },
+  F3: { en: "Exploring the data", it: "Esplorazione dei dati" },
+  F4: { en: "Planning the SQL", it: "Pianificazione della query" },
+  F5: { en: "Generating the SQL", it: "Generazione della query" },
+  F6: { en: "Validating the results", it: "Validazione dei risultati" },
+  F7: { en: "Reviewing with you", it: "Revisione con te" },
+  F8: { en: "Presenting results", it: "Presentazione dei risultati" },
+};
+
 type DotState = "done" | "running" | "error" | "pending";
 
 // Each state is a tinted chip; red is reserved strictly for error (the GSD theme's
@@ -39,9 +54,13 @@ export function WorkflowBar({
   const currentPhase = useSessionStore((s) => s.currentPhase);
   const phaseError = useSessionStore((s) => s.phaseError);
   const activeIdx = PHASES.findIndex((p) => p.id === currentPhase);
+  // On a finalized session all phases are done — surface the closing phase's title.
+  const titleId = finalized ? "F8" : currentPhase;
+  const phaseTitle = titleId ? PHASE_TITLES[titleId]?.[PHASE_LANG] : null;
 
   return (
-    <div className="flex items-center justify-center gap-3">
+    <div className="flex flex-col items-center gap-1">
+      <div className="flex items-center justify-center gap-3">
       <nav
         aria-label="Workflow progress"
         className="flex items-center gap-0 overflow-x-auto py-0.5"
@@ -99,6 +118,15 @@ export function WorkflowBar({
       })}
       </nav>
       <ElapsedTimer key={resetKey ?? "none"} running={running} />
+      </div>
+      {phaseTitle && (
+        <span
+          data-testid="phase-title"
+          className="text-[0.72rem] font-medium uppercase tracking-[0.12em] text-muted-foreground"
+        >
+          {phaseTitle}
+        </span>
+      )}
     </div>
   );
 }