Stop retrying unavailable thread subscriptions

[tim-smart]

Summary

• Distinguish deleted, archived, and temporarily missing threads when snapshot subscriptions fail.
• Stop client subscription retries for permanently unavailable deleted or archived threads while preserving retries for projection misses.
• Mark deleted threads as removed, retain cached archived-thread data, and add lifecycle-query coverage across server and client runtime tests.

Testing

• Added projection snapshot tests for active, archived, deleted, and missing thread lifecycle markers.
• Added server WebSocket tests for permanent deleted-thread failures and retriable missing-thread failures.
• Added client runtime tests confirming deleted and archived subscriptions stop retrying while missing threads continue retrying.