fix(updater): use GitHub atom feed for Beta lookup, dodge API rate limit

[appergb]

User description

Root cause

用户在 Beta-2 build 上点「加入 Beta 渠道」开关时显示「获取 Beta 版本信息失败」。现场 curl 实测：

```
HTTP/2 403
x-ratelimit-limit: 60
x-ratelimit-remaining: 0
{"message":"API rate limit exceeded for 103.62.49.154. ..."}
```

`api.github.com` 未认证调用是 60 req/h/IP——我之前 debug 调用 + 用户切 toggle 几次，同 IP 池就被耗尽了。在公司/家庭共享出口下，多个用户的 OpenLess 实例共用同一额度，更容易撞。

Fix

换成 `https://github.com/appergb/openless/releases.atom\`（公开 RSS，CDN cache，无 API rate limit）。

• atom feed 不显式标 `prerelease`，但项目约定 tag 后缀 `-beta-tauri` 必为 Beta，过滤后缀就够了
• timeout 10s → 15s
• 提取 `parse_latest_beta_from_atom` 纯函数，加两个 unit test：
  • 混合 stable + beta 时返回 Beta entry → ✅ pass
  • 全 stable 时返回 None → ✅ pass

Frontend not touched

JS 端 `invoke('fetch_latest_beta_release')` 签名 / 错误展示完全没动。Beta-3 build 装上后用户切 toggle 就直接生效。

Why atom over keeping API but adding auth

需要 GITHUB_TOKEN 注入到客户端——把任何 token 打进每个用户的 build 都不合理（公开二进制、token 要么暴露要么共享）。Atom feed 是无认证 + 无 rate limit 的天然解。

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PR Type

Bug fix, Tests

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Description

• Replace API call with Atom feed to avoid rate limit

• Increase timeout from 10s to 15s

• Parse feed with string matching, no XML lib

• Add tests for Beta tag detection

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Diagram Walkthrough

flowchart LR
  node1["api.github.com/releases (REST)"]
  node2["github.com/releases.atom (RSS)"]
  node3["parse_latest_beta_from_atom"]
  node4["LatestBetaRelease"]
  node1 -- "rate limit 60/h → 403" --> node2
  node2 -- "fetch & parse" --> node3
  node3 -- "filter by -beta-tauri suffix" --> node4

Loading

File Walkthrough

Relevant files

Bug fix

commands.rs Replace API with Atom feed for Beta release lookup              openless-all/app/src-tauri/src/commands.rs Replaced GitHub REST API call with Atom feed to avoid 60 req/h/IP rate limit Increased HTTP timeout from 10s to 15s for cross‑border networks Implemented parse_latest_beta_from_atom and extract_between for lightweight XML parsing Added unit tests: one for beta tag found, one for stable‑only feed returning none +98/-43

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[github-actions]

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