feat: add kickstart prompt and auto-compact context options

Kickstart Prompt:
- Remove Idle Timeout setting from respawn UI (uses 10s default)
- Add Kickstart Prompt field sent when /init doesn't trigger work
- New states: monitoring_init, sending_kickstart, waiting_kickstart
- Monitors 3s after /init to detect if Claude started working

Auto-Compact Context:
- Add auto-compact at 110k tokens (sends /compact with optional prompt)
- Preserves summarized context unlike /clear which wipes everything
- Optional focus prompt to guide what compact should preserve
- Blocks auto-clear while compacting to prevent conflicts

Also updates auto-clear default threshold from 100k to 140k tokens.

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

src/web/public/styles.css

@@ -21,6 +21,9 @@
 
 * { box-sizing: border-box; margin: 0; padding: 0; }
 
+/* Utility classes */
+.mt-sm { margin-top: 0.5rem; }
+
 body {
   font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
   background: var(--bg-dark);