Add validation to config loading with fallback to defaults for invalid localStorage data

[Copilot]

• Understand current config loading implementation
• Create validation functions for each config section (UI, editor, monaco, settings)
• Add type guards to validate loaded config structure
• Update loadConfig to use validation and fallback to defaults on invalid data
• Create tests for config loading with invalid values (26 test cases)
• Test with various invalid localStorage scenarios
• Address code review feedback (extract panel validation, support partial configs, fix formatting)
• Add documentation for validation functions
• Run security checks (manual review completed)
• Verify changes work correctly (build passes, all tests pass)
• Fix CI failures (added .npmrc with legacy-peer-deps)

Original prompt

Make config loading resistant to invalid values ( fallback to default config if needed )

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[bluesign]

@copilot check CI failures

[Copilot]

@copilot check CI failures

Fixed the CI failures. The issue was a peer dependency conflict between @types/react@19.2.7 and @fluentui/react@8.120.6 which requires @types/react <19.0.0.

Added .npmrc with legacy-peer-deps=true to resolve this during npm ci in CI. The workflow may require approval since it's triggered by a bot account. (commit c20144e)