Clean up legacy debt and fix linting errors

Legacy Debt Cleanup:
- Remove redundant .eslintrc.json (eslint.config.mjs is the active config)
- Fix unused variable linting error in template-engine.js

Linting:
- Remove unused error parameter in catch block (line 37)
- All linting checks now pass with no errors

This ensures clean code quality for v2.4.2 release.

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

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

Author: AssistantCompany

.eslintrc.json

@@ -34,7 +34,7 @@ function loadStackConfig() {
       GPT_MODEL: 'gpt-5',
       MCP_ENABLED: true,
     };
-  } catch (error) {
+  } catch {
     console.warn('Warning: Could not load stack config, using defaults');
     return {};
   }