docs: update egress control docs

[LSX-s-Software]

What

Clarify the egress control document and update stale examples.

Related issue

Closes #156

Scope and non-goals

Documentation

Design and behavior changes

None

Compatibility and operations

• Public API or generated protocol: N/A
• Configuration or defaults: N/A
• Snapshot manifest, artifact layout, or storage format: N/A
• Upgrade and rollback: N/A
• Host requirements, permissions, ports, or dependencies: N/A

Validation

• make fmt
• make clippy
• make test-unit
• Relevant Rust integration tests
• make -C services test (required when services/ changes)
• Generated clients/server regenerated with the documented make target
• Documentation updated
• Benchmarks or performance comparison completed

Skipped checks and reasons:

Doc changes only

Risks and reviewer notes

None

Checklist

• The PR contains one coherent change and no unrelated formatting or refactoring.
• New behavior is covered by tests, or I explained why testing is impractical.
• Logs and examples contain no credentials, tokens, or private registry information.
• I did not manually edit generated code without updating its source and regenerating it.

[github-actions]

✅ OpenCodeReview: Review skipped: no items were selected.