Update smoke tests for new features

[bburda]

Summary

Extend smoke tests to verify all new gateway v0.4.0 features in each demo.

Motivation

New features (plugins, scripts, triggers, logs, beacons) need automated verification in CI.

Proposed solution

New test assertions across all demos:

• Verify linux introspection data visible per entity (procfs/container info)
• Verify scripts API (list scripts, execute, check result)
• Verify triggers (create trigger, inject fault, verify event fires)
• Verify logs endpoint returns data

Sensor demo additional assertions:

• Verify beacon discovery (entity has beacon metadata)

Update smoke_lib.sh with new helper functions if needed.

Acceptance criteria

• All smoke tests pass on all 3 demos with new assertions
• CI green