fix: update mobile CSS for OpenCode run button group

Replace dead .btn-claude selectors in mobile.css with proper styling
for the new split run button (.btn-run + .btn-run-gear). Add mobile
touch-friendly dropdown menu options (10px padding, 35px height).
Include mode-specific colors for both Claude (blue) and OpenCode
(green) on mobile. Also guard Claude-specific features (Ralph,
Respawn) from running on OpenCode sessions in server.ts.

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

src/session.ts

@@ -1218,6 +1218,7 @@ export class Session extends EventEmitter {
     };
 
     // Forward to Ralph tracker to detect Ralph loops and todos
+    // (opencode sessions already returned early at line 1209)
     if (this._ralphTracker.enabled || !this._ralphTracker.autoEnableDisabled) {
       this._ralphTracker.processCleanData(getCleanData());
     }