fix(sessions): Top tools counts each tool call once

The session analysis page's Top tools list counted every event carrying a
tool_name, so each call was counted twice (its PreToolUse and its
PostToolUse) while the Tool calls total beside it counted once — a session
with 840 calls showed Bash at 1,533. The list now counts the same way as
the total: PreToolUse, or PostToolUse in a session with none (imported).

server/__tests__/ui-audit-routes.test.js

@@ -93,6 +93,12 @@ describe("GET /api/sessions/:id/stats tool totals", () => {
     assert.equal(body.tool_call_count, 2);
     assert.equal(body.distinct_tool_count, 1);
   });
+  it("counts each call once in tools_used, not its Pre and Post events", async () => {
+    const one = (await get("/api/sessions/ua-1/stats")).body.tools_used;
+    assert.ok(one.every((t) => t.count === 1));
+    const two = (await get("/api/sessions/ua-2/stats")).body.tools_used;
+    assert.deepEqual(two, [{ tool_name: "Read", count: 2 }]);
+  });
 });
 
 describe("GET /api/events labels", () => {

server/db.js

@@ -2547,10 +2547,16 @@ const stmts = {
     FROM events
     WHERE session_id = ? AND tool_name IS NOT NULL
   `),
+  // One row per call, like sessionToolCallTotals: a call is its PreToolUse,
+  // or its PostToolUse in a session that has none (imported). Counting every
+  // event with a tool_name counted each call twice.
   sessionToolUsageCounts: db.prepare(`
     SELECT tool_name, COUNT(*) as count
     FROM events
     WHERE session_id = ? AND tool_name IS NOT NULL
+      AND event_type = CASE
+        WHEN EXISTS (SELECT 1 FROM events WHERE session_id = ? AND event_type = 'PreToolUse')
+        THEN 'PreToolUse' ELSE 'PostToolUse' END
     GROUP BY tool_name
     ORDER BY count DESC
     LIMIT 15

server/routes/sessions.js

@@ -702,7 +702,7 @@ router.get("/:id/file", async (req, res) => {
 function sessionStats(sessionId) {
   const totalEvents = stmts.sessionEventCount.get(sessionId)?.count ?? 0;
   const eventsByType = stmts.sessionEventTypeCounts.all(sessionId);
-  const tools = stmts.sessionToolUsageCounts.all(sessionId);
+  const tools = stmts.sessionToolUsageCounts.all(sessionId, sessionId);
   // Exact totals: `tools_used` is a top-15 list, so its sum is not the count.
   // A tool call is a PreToolUse; a session with none (imported) counts PostToolUse.
   const toolTotals = stmts.sessionToolCallTotals.get(sessionId) || {};