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>

harness/.pi/extensions/gate/builders.js

@@ -102,10 +102,10 @@ function buildArtifactGate({ id, phase, title, artifact, action }) {
   }
   const ACTION_OPTIONS = {
     approve_reject: [
-      { id: "approve", label: "Conferma e prosegui", recommended: true },
+      { id: "approve", label: "Salva e procedi", recommended: true },
       { id: "reject", label: "Rifiuta" },
     ],
-    confirm: [{ id: "approve", label: "Conferma e prosegui", recommended: true }],
+    confirm: [{ id: "approve", label: "Salva e procedi", recommended: true }],
     view_only: [],
   };
   return {