test(performance): count startup phases and SQL statements for the J1 launch journey

Implements plan item A2. With IPTVNATOR_PERF_CAPTURE=1 the main process
keeps named counters and registers a main-only performance:read-counters
IPC handler; without the flag nothing is counted and the handler does not
exist.

- debug-trace.ts owns the registry; traceStartupPhase replaces the
  trace('startup', ...) sites and counts main.startupPhases.
- The database worker counts executed statements through better-sqlite3's
  Statement prototype (the verbose callback expands every statement and
  made bulk inserts 2-4x slower) and posts the count over its message
  port, flushed before every other worker message. The main-thread shared
  connection is counted through a new connection observer in the shared
  database library.
- The first main window freezes main.modulesRegisteredBeforeWindow at
  creation and main.sqlStatementsBeforeReadyToShow at ready-to-show.
- The journey gate drops the ready-to-show that Electron emits for the
  about:blank detour, so the app sees the real document's first paint,
  and taps the counters handler; the J1 record reads both counters after
  the renderer probe completes.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

libs/shared/database/README.md

@@ -28,6 +28,9 @@ import { content, categories, playlists, type Content } from '@iptvnator/shared/
 - `closeDatabase()` - Close connection
 - `getDatabasePath()` - Get database file path
 
+### Connection observer (`connection-observer.ts`)
+- `setDatabaseConnectionObserver(observer | null)` - Called by `initDatabase` with each connection it opens, before any statement runs on it. The Electron main process registers one only with `IPTVNATOR_PERF_CAPTURE=1`, to count main-thread SQL statements. The module has no runtime dependencies and is also importable as `@iptvnator/shared/database/connection-observer`.
+
 ## Database Location
 
 The SQLite database is stored at: `~/.iptvnator/databases/iptvnator.db`

libs/shared/database/src/index.ts

@@ -7,3 +7,4 @@
 export * from './lib/schema';
 export * from './lib/connection';
 export * from './lib/path-utils';
+export * from './lib/connection-observer';

libs/shared/database/src/lib/connection-observer.spec.ts

@@ -0,0 +1,30 @@
+import type Database from 'better-sqlite3';
+import {
+    notifyDatabaseConnectionOpened,
+    setDatabaseConnectionObserver,
+} from './connection-observer';
+
+describe('database connection observer', () => {
+    afterEach(() => {
+        setDatabaseConnectionObserver(null);
+    });
+
+    it('does nothing when no observer is registered', () => {
+        expect(() =>
+            notifyDatabaseConnectionOpened({} as Database.Database)
+        ).not.toThrow();
+    });
+
+    it('passes each opened connection to the registered observer until removed', () => {
+        const observer = jest.fn();
+        const first = { name: 'first' } as unknown as Database.Database;
+        const second = { name: 'second' } as unknown as Database.Database;
+
+        setDatabaseConnectionObserver(observer);
+        notifyDatabaseConnectionOpened(first);
+        setDatabaseConnectionObserver(null);
+        notifyDatabaseConnectionOpened(second);
+
+        expect(observer.mock.calls).toEqual([[first]]);
+    });
+});

libs/shared/database/src/lib/connection-observer.ts

@@ -0,0 +1,26 @@
+import type Database from 'better-sqlite3';
+
+export type DatabaseConnectionObserver = (
+    connection: Database.Database
+) => void;
+
+let observer: DatabaseConnectionObserver | null = null;
+
+/**
+ * Registers a callback that `initDatabase` calls with each connection it
+ * opens, before any statement runs on it; `null` removes it. The Electron
+ * main process uses it with IPTVNATOR_PERF_CAPTURE=1 to count main-thread
+ * SQL statements. This module has no runtime dependencies, so registering
+ * the observer does not load better-sqlite3.
+ */
+export function setDatabaseConnectionObserver(
+    next: DatabaseConnectionObserver | null
+): void {
+    observer = next;
+}
+
+export function notifyDatabaseConnectionOpened(
+    connection: Database.Database
+): void {
+    observer?.(connection);
+}

libs/shared/database/src/lib/connection.ts

@@ -23,6 +23,7 @@ import {
 } from '@iptvnator/shared/logging';
 import * as schema from './schema';
 import { getIptvnatorDatabasePath } from './path-utils';
+import { notifyDatabaseConnectionOpened } from './connection-observer';
 
 export type DatabaseInstance = BetterSQLite3Database<typeof schema>;
 
@@ -1228,6 +1229,7 @@ export async function initDatabase(
                 ? (message?: unknown) => traceSqlStatement(message)
                 : undefined,
         });
+        notifyDatabaseConnectionOpened(sqlite);
 
         if (isSqlTraceEnabled()) {
             traceSql('sql-main', 'open', {