fn parse_ts_from_name(fname: &str, channel_prefix: &str) -> Option<String>Expand description
Extract the timestamp segment from a snapshot dir name.
Format: <channel>-pre-v<code_version>-<ISO8601>.bak. We already know
the name starts with <channel>-pre-v (the caller checked); find the
last - before .bak to split off the timestamp from <code_version>.