insight-chat: ToolGateOpts + per-tool description rewrites

Tools whose backing tables are empty (calendar, location_history,
daily_summaries) drop out of the catalog so the LLM doesn't waste
iteration budget calling them only to receive "no results found".
Vision and apollo gates already existed; this generalizes the pattern.

search_messages gains start_ts/end_ts/contact_id filters (date filter
is a client-side post-filter; SMS-API only accepts contact_id natively
on the search endpoint).

Descriptions follow a consistent convention: one sentence (what +
when), param semantics, examples for tools with non-obvious param
choices. No more all-caps headers, no more identity-prescriptive
language inside descriptions.

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

src/database/daily_summary_dao.rs

@@ -75,6 +75,13 @@ pub trait DailySummaryDao: Sync + Send {
         context: &opentelemetry::Context,
         contact: &str,
     ) -> Result<i64, DbError>;
+
+    /// Get total count of all summaries (across all contacts). Used by
+    /// `current_gate_opts` to check whether daily_summaries are present.
+    fn get_total_summary_count(
+        &mut self,
+        context: &opentelemetry::Context,
+    ) -> Result<i64, DbError>;
 }
 
 pub struct SqliteDailySummaryDao {
@@ -454,6 +461,24 @@ impl DailySummaryDao for SqliteDailySummaryDao {
         })
         .map_err(|_| DbError::new(DbErrorKind::QueryError))
     }
+
+    fn get_total_summary_count(
+        &mut self,
+        context: &opentelemetry::Context,
+    ) -> Result<i64, DbError> {
+        trace_db_call(context, "query", "get_total_summary_count", |_span| {
+            let mut conn = self
+                .connection
+                .lock()
+                .expect("Unable to get DailySummaryDao");
+
+            diesel::sql_query("SELECT COUNT(*) as count FROM daily_conversation_summaries")
+                .get_result::<CountResult>(conn.deref_mut())
+                .map(|r| r.count)
+                .map_err(|e| anyhow::anyhow!("Count query error: {:?}", e))
+        })
+        .map_err(|_| DbError::new(DbErrorKind::QueryError))
+    }
 }
 
 // Helper structs for raw SQL queries