fix: Backfill project field on SDK session creation to prevent race condition

PostToolUse hook can create the session before UserPromptSubmit's
session-init sets the project, leaving it empty. Add an UPDATE after
INSERT OR IGNORE to backfill the project when a later hook provides it.

Closes #939

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/services/sqlite/SessionStore.ts

@@ -1165,7 +1165,7 @@ export class SessionStore {
     const now = new Date();
     const nowEpoch = now.getTime();
 
-    // Pure INSERT OR IGNORE - no updates, no complexity
+    // INSERT OR IGNORE to create session, then backfill project if it was created empty
     // NOTE: memory_session_id starts as NULL. It is captured by SDKAgent from the first SDK
     // response and stored via updateMemorySessionId(). CRITICAL: memory_session_id must NEVER
     // equal contentSessionId - that would inject memory messages into the user's transcript!
@@ -1175,6 +1175,14 @@ export class SessionStore {
       VALUES (?, NULL, ?, ?, ?, ?, 'active')
     `).run(contentSessionId, project, userPrompt, now.toISOString(), nowEpoch);
 
+    // Backfill project if session was created by another hook with empty project
+    if (project) {
+      this.db.prepare(`
+        UPDATE sdk_sessions SET project = ?
+        WHERE content_session_id = ? AND (project IS NULL OR project = '')
+      `).run(project, contentSessionId);
+    }
+
     // Return existing or new ID
     const row = this.db.prepare('SELECT id FROM sdk_sessions WHERE content_session_id = ?')
       .get(contentSessionId) as { id: number };