fix: restore 'won't be used' phrase in validation warnings for clarity

Restores the "won't be used" phrase in property visibility warnings to maintain
compatibility with existing tests and improve user clarity. The message now reads:
"Property 'X' won't be used - not visible with current settings"

This preserves the intent of the validation while keeping the familiar phrasing
that users and tests expect.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

src/services/config-validator.ts

@@ -539,7 +539,7 @@ export class ConfigValidator {
         warnings.push({
           type: 'inefficient',
           property: key,
-          message: `Property '${prop?.displayName || key}' is not visible with current settings`,
+          message: `Property '${prop?.displayName || key}' won't be used - not visible with current settings`,
           suggestion: visibilityReq || 'Remove this property or adjust other settings to make it visible'
         });
       }