fix(sandbox): real creds when no tls:terminate

[ericcurtin]

Summary

Without a tls: terminate endpoint in the sandbox policy, the proxy cannot intercept HTTPS traffic to rewrite credential placeholders in request headers. Placeholder values reached upstream APIs verbatim, causing 401 errors and immediate process exit (e.g. openshell sandbox create -- claude exiting right after the Claude Code wizard appeared).

Related Issue

N/A

Changes

• Skip placeholder mechanism when policy has no tls: terminate endpoints; pass real provider credentials directly to child process
• Emit a warning log directing operators to add protocol: rest and tls: terminate to HTTPS endpoints for secure credential rewriting
• Add has_tls_terminate_endpoints field to SandboxPolicy populated from the proto network policy at startup
• Update testdata/sandbox-policy.yaml to configure api.anthropic.com:443 with correct protocol, tls, and enforcement fields

Testing

• mise run pre-commit passes
• Unit tests added/updated (285 pass, 0 failed)
• E2E tests added/updated (if applicable)

Checklist

• Follows Conventional Commits
• Commits are signed off (DCO)
• Architecture docs updated (if applicable)

[johntmyers]

Thank you. Yes we've been discussing this. I created #533 which would solve for this as well.

[johntmyers]

We do not want to accept the risk of having secrets available to the child process and there are other corner cases where the manual setting of TLS termination has caused connection failures.