add reminder_stats field to stats Snapshot

Add Optional<ReminderStats> field to the per-agent stats page response,
placeholder for future ReminderRollup RPC integration to fetch reminder
activity metrics from the broker.

hive-ag3nt/src/stats.rs

@@ -14,6 +14,8 @@ use anyhow::{Context, Result};
 use rusqlite::{Connection, OpenFlags};
 use serde::Serialize;
 
+use hive_sh4re::ReminderStats;
+
 /// Window param accepted by `/api/stats?window=`. Each maps to a
 /// total span + the bucket width used to roll up trend series.
 #[derive(Debug, Clone, Copy)]
@@ -81,6 +83,11 @@ pub struct Snapshot {
     /// as the per-bucket fields but aggregated over the whole window
     /// for the headline summary chips.
     pub duration_summary: DurationSummary,
+    /// Reminder activity stats: counts of scheduled, delivered, and
+    /// pending reminders over the window (fetched from the broker RPC).
+    /// None if the RPC call failed or hasn't been integrated yet.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub reminder_stats: Option<ReminderStats>,
 }
 
 #[derive(Debug, Serialize)]
@@ -152,6 +159,7 @@ fn empty_snapshot(window: Window) -> Snapshot {
         result_mix: Vec::new(),
         models: Vec::new(),
         duration_summary: DurationSummary::default(),
+        reminder_stats: None,
     }
 }
 
@@ -250,6 +258,7 @@ fn snapshot(path: &Path, window: Window) -> Result<Snapshot> {
         result_mix: top_n(result_totals, 20),
         models,
         duration_summary,
+        reminder_stats: None, // TODO: fetch via ReminderRollup RPC
     })
 }