[Feature] Sidecar: safe defaults when no client/app (skip Specmatic)

[djm81]

Feature Description

Provide safe defaults for sidecar runs when no client/app is available, specifically around Specmatic execution.

Use Case

Primary Use Case: Brownfield Modernization

In Phase B validation, we often do not have a running service. We want sidecar runs to skip Specmatic by default or to make the skip explicit and easy.

Motivation

Specmatic attempts to start a stub or call a service, which can be unnecessary noise for validation runs focused on harness/CrossHair. Users should not need to remember to set RUN_SPECMATIC=0 each time.

Proposed Solution

• Add an option in sidecar init/run to set RUN_SPECMATIC=0
• Optional: detect missing target config and auto-skip Specmatic with a clear message
• Document the default behavior in the sidecar README

Alternative Solutions

Continue to require manual environment variables for every run.

Additional Context

We are skipping Specmatic in Phase B validation for Requests, Flask, and SpecFact CLI dogfooding.

Impact

• User Impact: Medium
• Complexity: Small
• Brownfield Relevance: Medium

Related Issues/PRs

• N/A

[djm81]

Related PR: #58

This PR includes code quality improvements to the sidecar templates, including run_sidecar.sh. While it doesn't implement the safe defaults for Specmatic skipping requested in this issue, it improves the maintainability of the sidecar scripts, which will make implementing the safe defaults feature easier.