feat: prefill new task from deep link

[cat-ph]

Summary

• add posthog-code://new?prompt=... deep links for prefilling the new task input
• queue links that arrive before the renderer subscription is ready
• redact deep-link query/hash content from logs

Test plan

• pnpm --filter @posthog/code exec vitest run src/main/services/new-task-link/service.test.ts src/main/services/inbox-link/service.test.ts src/main/services/deep-link/service.test.ts src/renderer/stores/navigationStore.test.ts
• pnpm --filter @posthog/code typecheck
• codex-review clean

[cat-ph]

closing in favor of the more complete #2173