fix(cleanup): prune mcp_tool_audit/a2a_task_events by created_at column (#9963)

Both tables (002_mcp_a2a_tables.sql) store their row timestamp in
created_at; the cleanup queries used WHERE timestamp < ? which does not
exist, so every boot-time cleanup logged:
  Error cleaning mcp_tool_audit: SqliteError: no such column: timestamp
  Error cleaning a2a_task_events: SqliteError: no such column: timestamp
and retention pruning for these two tables never ran. Fix the DELETE
columns and align the log labels/doc comments with the real table names.

Adds source-level invariant tests (cleanup-column-fix.test.mjs) asserting
the created_at column for both tables.

src/lib/db/cleanup.ts

@@ -164,7 +164,7 @@ export async function cleanupCompressionAnalytics(): Promise<CleanupResult> {
 }
 
 /**
- * Clean up old mcp_audit_log based on retention settings.
+ * Clean up old mcp_tool_audit based on retention settings.
  */
 export async function cleanupMcpAudit(): Promise<CleanupResult> {
   const db = getDbInstance();
@@ -178,15 +178,15 @@ export async function cleanupMcpAudit(): Promise<CleanupResult> {
   const result: CleanupResult = { deleted: 0, errors: 0 };
 
   try {
-    const stmt = db.prepare("DELETE FROM mcp_tool_audit WHERE timestamp < ?");
+    const stmt = db.prepare("DELETE FROM mcp_tool_audit WHERE created_at < ?");
     const runResult = stmt.run(cutoffISO);
     result.deleted = runResult.changes;
 
     console.log(
-      `[Cleanup] Deleted ${result.deleted} mcp_audit_log older than ${retentionDays} days`
+      `[Cleanup] Deleted ${result.deleted} mcp_tool_audit older than ${retentionDays} days`
     );
   } catch (err: unknown) {
-    console.error("[Cleanup] Error cleaning mcp_audit_log:", err);
+    console.error("[Cleanup] Error cleaning mcp_tool_audit:", err);
     result.errors++;
   }
 
@@ -194,7 +194,7 @@ export async function cleanupMcpAudit(): Promise<CleanupResult> {
 }
 
 /**
- * Clean up old a2a_events based on retention settings.
+ * Clean up old a2a_task_events based on retention settings.
  */
 export async function cleanupA2aEvents(): Promise<CleanupResult> {
   const db = getDbInstance();
@@ -208,13 +208,13 @@ export async function cleanupA2aEvents(): Promise<CleanupResult> {
   const result: CleanupResult = { deleted: 0, errors: 0 };
 
   try {
-    const stmt = db.prepare("DELETE FROM a2a_task_events WHERE timestamp < ?");
+    const stmt = db.prepare("DELETE FROM a2a_task_events WHERE created_at < ?");
     const runResult = stmt.run(cutoffISO);
     result.deleted = runResult.changes;
 
-    console.log(`[Cleanup] Deleted ${result.deleted} a2a_events older than ${retentionDays} days`);
+    console.log(`[Cleanup] Deleted ${result.deleted} a2a_task_events older than ${retentionDays} days`);
   } catch (err: unknown) {
-    console.error("[Cleanup] Error cleaning a2a_events:", err);
+    console.error("[Cleanup] Error cleaning a2a_task_events:", err);
     result.errors++;
   }
 

tests/unit/cleanup-column-fix.test.mjs

@@ -112,3 +112,29 @@ test("cleanup: memories uses correct table name (not 'memory_entries')", () => {
     "must NOT use non-existent table name memory_entries"
   );
 });
+
+test("cleanup: mcp_tool_audit prunes by created_at (existing column), not timestamp", () => {
+  // mcp_tool_audit has created_at (see 002_mcp_a2a_tables.sql); timestamp does
+  // not exist, so WHERE timestamp < ? raised SqliteError "no such column" at
+  // every boot-time cleanup and the retention pruning never ran.
+  assert.ok(
+    source.includes("DELETE FROM mcp_tool_audit WHERE created_at < ?"),
+    "mcp_tool_audit cleanup must use created_at column"
+  );
+  assert.ok(
+    !source.includes("DELETE FROM mcp_tool_audit WHERE timestamp"),
+    "must NOT use timestamp for mcp_tool_audit (column doesn't exist)"
+  );
+});
+
+test("cleanup: a2a_task_events prunes by created_at (existing column), not timestamp", () => {
+  // Same schema fact for a2a_task_events (created_at, no timestamp column).
+  assert.ok(
+    source.includes("DELETE FROM a2a_task_events WHERE created_at < ?"),
+    "a2a_task_events cleanup must use created_at column"
+  );
+  assert.ok(
+    !source.includes("DELETE FROM a2a_task_events WHERE timestamp"),
+    "must NOT use timestamp for a2a_task_events (column doesn't exist)"
+  );
+});