feat: add background AI sessions with persistent storage and SSE streaming

Introduces ai_sessions table (schema v9), AiSessionStore, and background
session support for mission interviews, planning, and subtask breakdown.
Adds BackgroundTasksIndicator component, SSE-based progress streaming,
and dashboard API routes for session management.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

package.json

@@ -5,7 +5,7 @@
   "type": "module",
   "packageManager": "pnpm@10.33.0",
   "scripts": {
-    "dev": "tsx packages/cli/src/bin.ts",
+    "dev": "pnpm build && tsx packages/cli/src/bin.ts",
     "dev:ui": "pnpm --filter @fusion/dashboard dev",
     "build": "pnpm -r build",
     "build:exe": "pnpm build && pnpm --filter @gsxdsm/fusion build:exe",