Make tests resilient to missing binaries and sandboxed environments

[pRizz]

Summary

This PR improves test reliability by making tests gracefully handle missing binaries and sandboxed/elevated environments where privileged port binding succeeds. It also ensures the Rust binary is built before running Node tests.

Changes

• Add cargo build -p opencode-cloud to the test-node justfile recipe to ensure the Rust binary is available before Node tests run
• Replace hard error in CLI parity tests with conditional skip when Rust binary is missing, with a helpful warning message logged at module load time
• Add can_bind_privileged_ports() helper function in both packages/cli-rust/src/commands/start.rs and packages/cli-rust/src/wizard/network.rs to detect sandboxed/elevated environments
• Update privileged port tests to skip gracefully when running in environments where privileged ports are bindable (root, sandboxed, or elevated capabilities), preventing false failures

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• Refactoring (no functional changes)

Testing

These changes improve test robustness:

• CLI parity tests now skip with a warning instead of failing when the Rust binary hasn't been built
• Privileged port tests skip in sandboxed/elevated environments instead of failing unexpectedly
• The test-node recipe now ensures the Rust binary is built before attempting to run tests

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings

Related Issues

Addresses test flakiness in CI/CD environments and sandboxed test runners.

https://claude.ai/code/session_01Nd43wo7HKi3qL4NHg9sRGD