5.9 Add end-to-end tests for the full trusted-session flow

[marwannettour]

Parent epic: #311

Summary

Cover complete trusted-session scenarios across invitation, acceptance, join, grants, and CLI waiting.

Requirements

• Test A invites B, B accepts manually, and B joins.
• Test A invites B, B auto-accepts through a grant, and B joins.
• Test inventory mode.
• Test synchronize mode rejection with insufficient grant.
• Test invitation expiration before acceptance.
• Test accepted invitation with join failure.
• Test multiple recipients with mixed outcomes.
• Test CLI --wait exit codes.

Acceptance criteria

• End-to-end tests cover the main happy paths and failure paths.
• Tests verify CLI result codes and status output.