OperServ: INFO staff notes on accounts and channels

INFO ADD <target> <note> / DEL <target> / <target> attaches a staff note
to an account or channel (a #name is a channel, else an account). The note
is shown in that service's INFO — but to operators only (Priv::Auspex),
never to the account's own owner. Admin-only to set.

Follows the typed-field-on-the-entity pattern: an oper_note field folded
through AccountOperNoteSet (Global) / ChannelOperNoteSet (Local) events,
read via dedicated Store getters so it stays out of the public views and
the directory feed.

operserv/src/info.rs

@@ -0,0 +1,53 @@
+use fedserv_api::{Priv, Sender, ServiceCtx, Store};
+
+// INFO <target> | INFO ADD <target> <note> | INFO DEL <target>: attach a staff
+// note to an account or channel (a `#name` is a channel, else an account). The
+// note is shown to operators in that service's INFO. Admin-only.
+pub fn handle(me: &str, from: &Sender, args: &[&str], ctx: &mut ServiceCtx, db: &mut dyn Store) {
+    if !from.privs.has(Priv::Admin) {
+        ctx.notice(me, from.uid, "Access denied — INFO needs the \x02admin\x02 privilege.");
+        return;
+    }
+    match args.get(1).map(|s| s.to_ascii_uppercase()).as_deref() {
+        Some("ADD") | Some("SET") => set(me, from, args.get(2).copied(), args.get(3..).unwrap_or(&[]), ctx, db),
+        Some("DEL") | Some("CLEAR") => set(me, from, args.get(2).copied(), &[], ctx, db),
+        Some(_) => show(me, from, args[1], ctx, db),
+        None => ctx.notice(me, from.uid, "Syntax: INFO <target> | INFO ADD <target> <note> | INFO DEL <target>"),
+    }
+}
+
+// `note` empty clears; otherwise it's the joined note words.
+fn set(me: &str, from: &Sender, target: Option<&str>, note: &[&str], ctx: &mut ServiceCtx, db: &mut dyn Store) {
+    let Some(target) = target else {
+        ctx.notice(me, from.uid, "Syntax: INFO ADD <target> <note> | INFO DEL <target>");
+        return;
+    };
+    let text = note.join(" ");
+    let value = if text.trim().is_empty() { None } else { Some(text) };
+    let (ok, kind) = if target.starts_with('#') || target.starts_with('&') {
+        (db.set_channel_note(target, value.clone()), "channel")
+    } else if let Some(account) = db.resolve_account(target).map(str::to_string) {
+        (db.set_account_note(&account, value.clone()), "account")
+    } else {
+        (false, "account")
+    };
+    if !ok {
+        ctx.notice(me, from.uid, format!("There's no {kind} \x02{target}\x02."));
+    } else if value.is_some() {
+        ctx.notice(me, from.uid, format!("Staff note set on \x02{target}\x02."));
+    } else {
+        ctx.notice(me, from.uid, format!("Staff note on \x02{target}\x02 cleared."));
+    }
+}
+
+fn show(me: &str, from: &Sender, target: &str, ctx: &mut ServiceCtx, db: &mut dyn Store) {
+    let note = if target.starts_with('#') || target.starts_with('&') {
+        db.channel_note(target)
+    } else {
+        db.resolve_account(target).map(str::to_string).and_then(|a| db.account_note(&a))
+    };
+    match note {
+        Some(n) => ctx.notice(me, from.uid, format!("Staff note on \x02{target}\x02: {n}")),
+        None => ctx.notice(me, from.uid, format!("No staff note on \x02{target}\x02.")),
+    }
+}