refactor(web_ui): Bus::effective_context_window, sigint_claude + per-connection hello, relocate fetch_reminder_stats, drop redundant guard

hive-ag3nt/src/events.rs

@@ -901,6 +901,16 @@ impl Bus {
         *self.api_context_window.lock().unwrap()
     }
 
+    /// The effective context window for `model`: the API-reported window if a
+    /// turn has completed ([`api_context_window`]), else the per-model default
+    /// ([`context_window_tokens`]). Single accessor so the state + dashboard
+    /// endpoints agree by construction.
+    #[must_use]
+    pub fn effective_context_window(&self, model: &str) -> u64 {
+        self.api_context_window()
+            .unwrap_or_else(|| context_window_tokens(model))
+    }
+
     /// Walk a stream-json value for `tool_use` blocks and bump the
     /// per-turn counter for each one we find. Called by the stdout
     /// pump on every parsed line. Cheap when the line isn't an