The dashboard showed a sing-box version that never changed. build_system_info()
preferred /etc/tachyon/sing-box-version for every "extended" variant, and that
state file is written by the component action alone — a sing-box installed via
install.sh, opkg or by hand leaves it pinned at whatever was recorded last. The
UI then reported the stale version indefinitely, and the update badge compared
the release against it rather than against the binary actually on disk.
The state file only exists for variants whose binary cannot be executed to print
a version: extended-compressed is a self-extracting stub, and lx needs a runtime
that may be absent. Plain extended answers `sing-box version` fine — singbox
/runtime.uc:259 and subscription/cache.uc:1482 both gate on the compressed
variants only. Covering plain extended was a regression from 46ef97fe.
Both call sites now share sing_box_resolved_version(), which also falls through
to the live probe when the state file is missing or empty instead of reporting
"unknown".
Verified on a router: with the state file still holding 1.13.16-extended-2.6.2,
system-info now reports the installed 1.13.18-extended-2.6.3.
