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/__tests__/builders.test.js

@@ -167,7 +167,7 @@ test("buildArtifactGate derives approve/reject options from action.kind", () =>
     action: { kind: "approve_reject" },
   });
   assert.deepEqual(w.options, [
-    { id: "approve", label: "Conferma e prosegui", recommended: true },
+    { id: "approve", label: "Salva e procedi", recommended: true },
     { id: "reject", label: "Rifiuta" },
   ]);
 });
@@ -176,7 +176,7 @@ test("buildArtifactGate: confirm -> single approve; view_only -> no options", ()
   const confirm = buildArtifactGate({
     id: "u1", phase: "F1", title: "t", artifact: { kind: "phase", data: {} }, action: { kind: "confirm" },
   });
-  assert.deepEqual(confirm.options, [{ id: "approve", label: "Conferma e prosegui", recommended: true }]);
+  assert.deepEqual(confirm.options, [{ id: "approve", label: "Salva e procedi", recommended: true }]);
   const viewOnly = buildArtifactGate({
     id: "u1", phase: "F1", title: "t", artifact: { kind: "phase", data: {} }, action: { kind: "view_only" },
   });