[Trenyx]

Closes #1100

Tests only: five unit tests (+70 lines) in the existing test modules. No change to library code, no new dependencies.

Test	What it pins down
tests::node_idx_wraps_past_last_point (pingora-ketama)	A hash above the last ring point wraps to the first point
selection::consistent::test::test_ketama_honors_backend_weight (pingora-load-balancing)	A weight 3 backend takes its weighted share of the ring
health_check::test::test_health_counter_restarts_after_flip (pingora-load-balancing)	After a flip, flipping back takes the full threshold again
connection::tests::test_pool_node_remove_keeps_other_hot_queue_items (pingora-pool)	PoolNode::remove keeps the items queued ahead of its target
eviction::lru::test::test_peek_does_not_promote (pingora-cache)	peek leaves the eviction order alone, as EvictionManager::peek documents

How they were checked

On a copy at 1adcb38 (current main):

• With the tests added to unchanged code, cargo fmt --all -- --check, cargo clippy --all-targets -p <crate> -- --allow=unknown-lints --deny=warnings and cargo test -p <crate> for the four crates all pass (pingora-ketama 7, pingora-load-balancing 81, pingora-pool 36 and pingora-cache 221 unit tests, including the new ones).
• With each of the five bugs from the issue applied one at a time, exactly its matching test fails and every other test still passes.

These tests were written with Claude Code during a planted-bug run by SK @ Trenyx.