[unsupervised AI] Fix late worker alias restrictions

[AG0708]

Summary

• resolve worker-name aliases that connect after task submission to their exact worker address
• prevent a late alias from incorrectly expanding the restriction to every worker on the same host
• add a scheduler regression test covering mixed present and late worker names

Validation

• distributed/tests/test_scheduler.py — 475 passed, 43 skipped, 1 expected xfail
• focused late-worker regression — red on the base commit, green with this change
• Ruff 0.15.16 lint and formatting checks — passed
• git diff --check — passed

Closes #8862

[github-actions]

Unit Test Results

See test report for an extended history of previous test failures. This is useful for diagnosing flaky tests.

    40 files  +    1      40 suites  +1   14h 45m 25s ⏱️ + 17m 44s
 4 160 tests +    1   3 978 ✅  -     2    178 💤 ±  0  4 ❌ +3 
80 959 runs  +2 731  76 719 ✅ +2 588  4 236 💤 +140  4 ❌ +3 

For more details on these failures, see this check.

Results for commit f226a45. ± Comparison against base commit 40fcd99.