fix: treat dropped connection as success in restart handler

The Supervisor kills our process while the restart request is in
flight, causing httpx to throw ReadError/RemoteProtocolError. That's
actually the SUCCESS path — the restart is happening. Catch those
specifically and return success.

Also surface the real Supervisor error message in the browser when a
real failure occurs (was showing generic "Restart failed" before).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: kingpanther13

src/ha_mcp/settings_ui.py

@@ -380,11 +380,18 @@ def apply_tool_visibility(
     if (resp.ok) {
       btn.textContent = 'Restart initiated — reload page in ~30s';
     } else {
-      btn.textContent = 'Restart failed';
+      let msg = 'Restart failed';
+      try {
+        const err = await resp.json();
+        if (err.error && err.error.message) msg = 'Failed: ' + err.error.message;
+      } catch (_e) {}
+      btn.textContent = msg;
       btn.disabled = false;
+      alert(msg);
     }
   } catch (_e) {
-    btn.textContent = 'Connection lost (expected during restart)';
+    // Connection lost mid-request is actually expected — the addon is restarting
+    btn.textContent = 'Restart initiated (connection dropped)';
   }
 }
 
@@ -672,24 +679,38 @@ async def _restart_addon(_: Request) -> JSONResponse:
                 {"success": False, "error": {"code": "NOT_IN_ADDON", "message": "Restart only available in add-on mode"}},
                 status_code=400,
             )
+        # Short timeout — the supervisor kills our process during restart so
+        # the connection will drop. A connection drop is actually success.
         try:
-            async with httpx.AsyncClient(timeout=10.0) as client:
+            async with httpx.AsyncClient(timeout=5.0) as client:
                 resp = await client.post(
                     "http://supervisor/addons/self/restart",
                     headers={"Authorization": f"Bearer {token}"},
                 )
-            if resp.status_code >= 400:
-                logger.error("Supervisor restart failed: %d %s", resp.status_code, resp.text)
-                return JSONResponse(
-                    {"success": False, "error": {"code": "SUPERVISOR_ERROR", "message": f"Supervisor returned {resp.status_code}"}},
-                    status_code=502,
-                )
+        except (httpx.ReadError, httpx.RemoteProtocolError, httpx.ConnectError):
+            # Connection dropped mid-request — restart is happening
+            logger.info("Restart request connection dropped (expected during restart)")
+            return JSONResponse({"success": True, "message": "Restart initiated"})
         except httpx.HTTPError as e:
             logger.exception("Failed to reach Supervisor for restart")
             return JSONResponse(
                 {"success": False, "error": {"code": "SUPERVISOR_UNREACHABLE", "message": str(e)}},
                 status_code=502,
             )
+
+        if resp.status_code >= 400:
+            body = resp.text
+            logger.error("Supervisor restart failed: %d %s", resp.status_code, body)
+            return JSONResponse(
+                {
+                    "success": False,
+                    "error": {
+                        "code": "SUPERVISOR_ERROR",
+                        "message": f"Supervisor returned {resp.status_code}: {body[:500]}",
+                    },
+                },
+                status_code=502,
+            )
         return JSONResponse({"success": True, "message": "Restart initiated"})
 
     @mcp.custom_route("/api/settings/info", methods=["GET"])