release: a3s 0.10.15

[ZhiXiao-Lin]

Summary

• bump the CLI and lockfile to 0.10.15
• publish the legacy self-update compatibility fix merged in fix(update): restore legacy self-update compatibility #66
• document that the Anthropic SRT runtime remains removed

Validation

• release-state script tests passed
• release state is consistent for CLI 0.10.15, Core 6.5.2, TUI 0.1.14, and Search 2.1.0
• compatibility PR CI passed on Linux, macOS, and Windows: https://github.com/A3S-Lab/CLI/actions/runs/30415885325
• public v0.10.8 binary completed the controlled end-to-end self-update through the bridge