Enable thinking selector in MessageEditor

- Import Select component from mini-lit and Brain icon from lucide
- Add thinkingLevel property to track current thinking level (off/minimal/low/medium/high)
- Enable showThinkingSelector (was disabled before)
- Add onThinkingChange callback for thinking level changes
- Render Select component with thinking level options when model supports reasoning
- Position thinking selector on left side next to attachment button
- Add i18n translations for Off/Minimal/Low/Medium/High in English and German
- Rename showThinking → showThinkingSelector in AgentInterface and ChatPanel for consistency
- Remove showDebugToggle property from AgentInterface (unused)
- Clean up browser-javascript tool output message (remove CSP note)

packages/browser-extension/src/tools/browser-javascript.ts

@@ -309,9 +309,7 @@ This ensures reliable execution.`,
 				);
 
 				return {
-					output:
-						output.trim() ||
-						"Code executed successfully (no output)\n\n⚠️ Note: CSP blocked direct execution. Code ran via JailJS interpreter.",
+					output: output.trim() || "Code executed successfully (no output)",
 					isError: false,
 					details: { files },
 				};