Harden guardrail routing and imported pricing

[gcjordi]

Summary

• Make branching Guardrails fail closed unless an exact route is configured.
• Flag missing or invalid Guardrail routes in the Architecture Analyzer.
• Preserve legitimate imported pricing only after explicit user confirmation.
• Preserve trusted locally stored per-node price overrides.
• Add regression coverage for Guardrail routing, imported pricing, and three-level nested loops with Merge.

Validation

• 34 core tests pass locally.
• JavaScript syntax checks pass for all modified runtime files.
• No new dependency, backend, API key, secret, or external data transmission.
• Catalan, Spanish, and English are included for the new confirmation text.
• Full browser test suite could not be executed in the current environment because its browser binary is unavailable.

Scope

The change is confined to the analyzer, importer, model validation, simulator, local storage validation, and regression tests. No schema version or external dependency changes.