fix: prevent agents from running indefinitely after app quit

Agents kept running after closing AgentCompany because worker processes
auto-recreated on exit, retry timers were never cleared, child CLI
processes weren't terminated, and orchestration had no quit guards.

Changes:
- Add isQuitting guards to all orchestration/automation entry points
- Track and clear all setTimeout/setInterval timers on quit
- Send cancel-run to all active CLI processes before killing worker
- Add destroyed flag to prevent worker recreation after intentional destroy
- Add quit confirmation dialog: Stop All & Quit / Minimize to Background / Cancel
- Bump version to 0.4.96

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

package.json

@@ -1,6 +1,6 @@
 {
   "name": "agent-company",
-  "version": "0.4.95",
+  "version": "0.4.96",
   "private": true,
   "type": "module",
   "description": "Cross-platform Electron desktop control plane for local-first AI agent companies.",