dashboard — bouton live (viser natif demo.py) + PLY (fallback viser_ply)

live button:
- POST /jobs/{id}/live
- Probe le port natif (worker viser_port_base + job_id) via nc
- 200 + viser_url si demo.py encore alive (necessite le patch keep-alive)
- 410 + fallback message si ferme

PLY button:
- POST /jobs/{id}/view (existant)
- Lance viser_ply.py standalone sur port VIEWER_PORT_BASE+id

Permet de choisir entre viser natif (PointCloudViewer de lingbot-map avec
camera frustums, filtre confiance interactif, animation) et viewer basic
XYZ+RGB uniquement.

app/main.py

@@ -375,6 +375,31 @@ async def view_job(job_id: int):
     return {"url": f"http://{worker['host']}:{port}"}
 
 
+@app.post("/jobs/{job_id}/live")
+async def live_job(job_id: int):
+    """Return the URL of demo.py's native viser (PointCloudViewer with camera frustums,
+    confidence filtering, animation) if it's still listening. Otherwise 404 so the UI falls
+    back to /view (viser_ply.py standalone)."""
+    with closing(db()) as conn:
+        row = conn.execute(
+            "SELECT viser_url, worker_host FROM jobs WHERE id=? AND status='done'",
+            (job_id,),
+        ).fetchone()
+    if not row or not row["viser_url"]:
+        raise HTTPException(404, "viser natif jamais démarré")
+    worker = _worker_by_host(row["worker_host"]) or WORKERS[0]
+    native_port = worker["viser_port_base"] + job_id
+    proc = await asyncio.create_subprocess_exec(
+        "ssh", "-o", "BatchMode=yes", "-o", "ConnectTimeout=3", worker["ssh_alias"],
+        f"nc -z -w2 127.0.0.1 {native_port}",
+        stdout=asyncio.subprocess.DEVNULL, stderr=asyncio.subprocess.DEVNULL,
+    )
+    await proc.wait()
+    if proc.returncode != 0:
+        raise HTTPException(410, "viser natif fermé — utilise le bouton PLY")
+    return {"url": row["viser_url"]}
+
+
 @app.post("/stitches/{stitch_id}/view")
 async def view_stitch(stitch_id: int):
     with closing(db()) as conn: