ci-queue: Recover when the Redis queue master dies during setup

[kstewartfigma]

Summary

Fixes the longstanding failure mode discussed in Slack: if the worker elected to populate the Redis queue dies while master-status is setup, every surviving worker currently waits until it raises CI::Queue::Redis::LostMaster.

• replace the permanent setup marker with a renewable, generation-owned Redis lease
• let surviving workers detect an expired setup lease and retry leader election
• fence queue publication and chunk metadata writes with compare-and-set Lua scripts so a stale master cannot overwrite its replacement
• publish the complete queue and ready status atomically
• bound recovery attempts with configurable defaults

Proof

Added regression coverage for:

• a surviving worker taking over after the original master dies during setup
• a stale master being unable to overwrite the replacement queue
• lease renewal during slow queue population

Validation:

• 161 tests, 603 assertions, 0 failures across the complete test/ci/queue unit suite
• gem build succeeds and includes the three new Lua scripts
• git diff --check passes

Local Ruby 3.4 still has the repository's six existing RSpec output-fixture failures caused by Ruby 3.4 changing backtrace quoting. The repository's CI matrix intentionally runs Ruby 3.0–3.3.

[kstewartfigma]

Codex update: reviewed the failed Ruby matrix and fixed it in 679d4f9.

All four jobs failed in Integration::MinitestRedisTest#test_down_redis: the new follower wait attempted another Redis read after election had already encountered a connection error, bypassing ci-queue's existing graceful behavior when Redis is completely unavailable.

The fix routes only that follower wait through the existing rescue_connection_errors helper. Master-side connection failures, expired setup leases, and stale-master fencing still fail loudly.

Verification:

• exact formerly failing test: 1 test, 3 assertions, 0 failures
• complete test/ci/queue suite: 161 tests, 603 assertions, 0 failures
• GitHub matrix: Ruby 3.0, 3.1, 3.2, and 3.3 all passing