fix(journal): preserve archives when rolls share a timestamp

[belowzeroff]

How it looks from the user's side

A service rolls its journal twice during the same UTC second.

Before - both rolls target the same base.YYYY.MM.DDTHH.MM.SSZ.log path, so the second roll replaces the first archive and its journal entries are lost.

After - the first archive keeps the timestamped name and subsequent collisions use unique names such as base.YYYY.MM.DDTHH.MM.SSZ.1.log, preserving every segment.

Root cause

ray_journal_roll generated archive names with second-level precision and passed them to rename(), which replaces an existing destination.

Fix

Probe the timestamped archive path before closing the journal. If it already exists, append an incrementing numeric suffix until an unused path is found.

Tests

• ./rayforce.test --filter journal/roll_twice
• make test with the repository's non-ASAN debug flags
• Result: 3779 of 3780 passed, 1 skipped, 0 failed