insight-chat: code-review polish on the tool-gating PR

- search_messages now delegates to search_messages_with_contact(.., None)
  so the two methods share a single HTTP path. Drops the dead-code
  warning and the ~30-line duplication.
- DailySummaryDao gains has_any_summaries (LIMIT 1 existence probe)
  used by current_gate_opts; the SELECT COUNT(*) get_total_summary_count
  added in the prior commit is removed (it had no other caller).
- current_gate_opts doc comment corrected to describe what the probes
  actually do.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/ai/insight_generator.rs

@@ -144,10 +144,13 @@ impl InsightGenerator {
     }
 
     /// Compute the per-call tool gate options by probing each backing
-    /// table. Cheap (`SELECT 1 FROM <t> LIMIT 1` shape via the existing
-    /// count methods); meant to be called once per chat turn / generation.
-    /// `has_vision` is supplied by the caller because it depends on the
-    /// model selected for this turn, not on persistent state.
+    /// table for presence. `daily_summaries_present` uses a `LIMIT 1`
+    /// existence probe; `calendar_present` and `location_history_present`
+    /// use the existing `get_event_count` / `get_location_count`
+    /// methods (small enough that a full `COUNT(*)` is fine). Meant to
+    /// be called once per chat turn / generation. `has_vision` is
+    /// supplied by the caller because it depends on the model selected
+    /// for this turn, not on persistent state.
     pub fn current_gate_opts(&self, has_vision: bool) -> ToolGateOpts {
         let cx = opentelemetry::Context::new();
         let calendar_present = {
@@ -169,9 +172,7 @@ impl InsightGenerator {
                 .daily_summary_dao
                 .lock()
                 .expect("Unable to lock DailySummaryDao");
-            dao.get_total_summary_count(&cx)
-                .map(|n| n > 0)
-                .unwrap_or(false)
+            dao.has_any_summaries(&cx).unwrap_or(false)
         };
         ToolGateOpts {
             has_vision,