fix(compiler): skip invalid contract routes in conflict checks

[cssbruno]

Summary

• Prevent invalid generated contract routes from also entering route conflict validation.
• Keeps the specific contract_route_invalid diagnostic ahead of broader route_method_conflict noise when a contract method/path is invalid.
• Fixes the final combined go test ./... regression after the M2 compiler PR merge chain.

Verification

• go test ./internal/compiler
• go test ./...
• go build ./cmd/gowdk

LLM Assistance

• Implemented by Codex after the final M2 merge audit exposed the integration failure.