Fix flaky session replica consistency test

[guivieiras]

The session replica test can compare old messages before new events arrive because both timelines have the same entry and turn counts. This caused intermittent Linux CI failures.

Wait for the second turn’s completion event before comparing contents. The existing assertion still checks that the replica matches the live timeline. Only the test changes.

Validation:

• Updated test passed 20 consecutive runs.
• Workspace formatting, build, tests, and dependency checks passed.
• Strict workspace Clippy reports five existing warnings in command_validation.rs, store/mod.rs, and terminal_drawer.rs, outside this change.
• Other platform checks are left to CI; this change is confined to a desktop test.