[CI] Remote machine provider fails to connect an agent within 45 minutes

## Failure signature

Azure jobs are canceled before any task starts with:

```text
Remote machine provider issue: The agent did not connect within the alloted time of 45 minute(s).
```

## Confirmed occurrences

| PR / head | Build and job | Outcome |
|---|---|---|
| #26203 / `abd0ea0058d6285dccbdcc9c0fc4837d264b45d0` | [14718863 - arm64 Mac Golden Gate (27)](https://devdiv.visualstudio.com/DevDiv/_build/results?buildId=14718863&view=logs&jobId=9f06bed7-d307-565d-19e9-ea648dcaf303) | No agent connected within 45 minutes. The separately accepted stage attempt 2 succeeded. |
| #26131 / `067c0f36f6aed495bc0b54f4cebe08ca41e9e0bb` | [14731458 - linker_maccatalyst](https://devdiv.visualstudio.com/DevDiv/_build/results?buildId=14731458&view=logs&jobId=dc49fd7f-b39a-580f-b9a6-2209b7abaf55) | No agent connected; build remains active, so no retry has been submitted. |

First observed: 2026-07-21 19:22 UTC. Latest observed: 2026-07-22 13:55 UTC. Recurrence: 2 jobs across 2 distinct monitored PRs.

## Classification and impact

This is a CI infrastructure failure in the remote machine provider. The affected job never receives a worker and executes no repository task, so otherwise unrelated PRs are blocked by a terminal canceled check.

## Investigation

- Inspected the Azure timeline records and exact job issues for both builds.
- Confirmed the current #26131 job has no worker name, task logs, or executed child tasks.
- Confirmed the #26203 retry succeeded, demonstrating that the source/build was not the cause.
- Searched all open and closed `dotnet/macios` issues using the exact message, `Remote machine provider issue`, the 45-minute text, and AcesShared terminology; no matching issue was found.

## Workaround

After the build is terminal, the PR is conflict-free, retry accounting is reconciled, and no equivalent attempt is active, rerun the failed job/stage. Azure diagnostic artifacts and timelines have limited retention.

Start with the Azure timeline records and exact job issues for builds 14718863 and 14731458, comparing the failed attempts with the separately accepted retry. The payload names no source files or tests; done requires identifying a provider-side cause or a verified remediation for jobs that fail to connect an agent within 45 minutes.

Written by the indexing model from the issue text.