Add ChanFix: recover opless channels from op-time scores

The engine samples live op state on a short cadence, scoring op-time per
identity (account, else host) on the network view — a net +1 per pass
while opped, -1 while idle, so trusted regulars rise and stale ops fade.
ChanFix (operator-only) reads those scores: SCORES <#chan> shows the
standings, CHANFIX <#chan> reops the present regulars scoring above a
share of the top score, once the channel is opless enough and has real
history. It defers to ChanServ — a registered channel is refused. Opt-in.

C++ note: the original persists scores to the services DB and runs its own
timers; here scoring rides the existing periodic loop and lives on the
ephemeral network view, so it's node-local and rebuilds itself.

api/src/lib.rs

@@ -1027,6 +1027,10 @@ pub trait NetView {
     // Session limiting: live sessions from an IP, and IPs at/over a threshold.
     fn session_count(&self, ip: &str) -> u32;
     fn sessions_over(&self, min: u32) -> Vec<(String, u32)>;
+    // ChanFix: op-time scores (identity -> score, highest first) and the current
+    // op count for a channel.
+    fn chanfix_scores(&self, channel: &str) -> Vec<(String, u32)>;
+    fn op_count(&self, channel: &str) -> usize;
     // Search the recent moderation/action incident log (newest first, capped at
     // `limit`). An empty pattern returns the most recent; otherwise matches the
     // id or a case-insensitive substring of the summary.