fix(release): stable 仅发布正式版本，修复 4.28.0 被 beta 阻塞

[Soulter]

定时发布使用 sort -V 选择最新上游标签，会将 v4.28.0-beta.1 排在 v4.28.0 之后。由于 beta 的 Desktop Release 已存在，任务持续跳过正式版构建；beta 也会被作为 stable 发布。

Summary / 改动概述

• tag-poll 在排序前只保留 vMAJOR.MINOR.PATCH 正式标签，排除 alpha、beta、rc、dev、nightly 等后缀及其他非正式标签；没有正式标签时明确失败。
• 手动 tag-poll 使用相同规则校验 source_git_ref，防止通过手动入口将预发布版本发布到 stable。预发布标签、分支和 commit 需改用 custom。
• 更新 workflow 输入说明和发布文档，补充正式版与预发布版共存、已有正式版、无正式标签、手动覆盖及 Latest 标记的回归测试。

Verification / 验证方式

使用带 TOML 支持的 Python 环境完成本地验证：

pnpm run test:prepare-resources
188 tests passed, 0 failed

python3 -m unittest discover -s scripts/ci -p 'test_*.py'
Ran 91 tests — OK

bash -n scripts/ci/resolve-build-context.sh
git diff --check
Passed

使用真实上游标签验证筛选逻辑，最新正式版正确解析为 v4.28.0。

相关 Actions：修复前的定时发布任务，日志显示选择 v4.28.0-beta.1 并输出 Build enabled: false，各平台构建及发布均被跳过。

本 PR 尚未触发安装包发布，也未修改现有 Release 或线上 stable manifest。

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Checklist / 检查清单

• This change is not a breaking change. / 此改动不是破坏性变更。手动 tag-poll 输入有意收紧为正式版本标签；原分支、commit 和预发布输入需迁移至 custom。
• I have verified the change locally (and provided logs/screenshots above). / 我已在本地验证并在上方提供日志/截图。
• If workflows are changed, I attached at least one related Actions run link. / 如果修改了工作流，我已附上至少一个相关 Actions 运行链接。
• If dependencies are updated, lockfiles are updated accordingly. / 本 PR 未修改依赖或 lock 文件。
• This PR does not include malicious code. / 此 PR 不包含恶意代码。

Summary by Sourcery

Restrict stable release polling to formal version tags and prevent prerelease sources from entering the stable channel.

Bug Fixes:

• Ensure stable tag polling selects and publishes the latest formal vMAJOR.MINOR.PATCH release instead of being blocked by prerelease tags.
• Reject prerelease tags, branches, and commit references supplied through manual stable tag-poll runs.

Enhancements:

• Clarify workflow and development documentation for stable versus prerelease publishing, including behavior when releases already exist or no stable tags are available.

Tests:

• Add regression coverage for stable tag selection, prerelease filtering, missing stable tags, manual override validation, and Latest release marking.

[sourcery-ai]

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