* fix(router): discard oldest entry when trimming latency list in lowest_latency strategy
The lowest_latency routing strategy keeps a rolling window of the most
recent latency and time-to-first-token measurements per deployment. When
the window is full, the strategy was discarding the *newest* value
instead of the oldest, because the trim used
`[: max_latency_list_size - 1]` (keeping indices 0..N-2) rather than
`[1:]` (dropping index 0 and keeping indices 1..N-1).
Since new values are appended at the end, the bug meant the most recent
measurement was always dropped once the list reached capacity. The
routing decisions then relied on stale data (including any early-spike
values that never aged out), and timeout penalties written via
`async_log_failure_event` were silently discarded as well.
Fix the slice in all five call sites (sync + async log_success_event for
both latency and time_to_first_token, and async_log_failure_event for
the timeout penalty) and add regression tests covering each path.
* test(router): cover async TTFT trim path in lowest_latency regression tests
Adds test_ttft_list_trimming_discards_oldest_entry_async, an async
counterpart to test_ttft_list_trimming_discards_oldest_entry that drives
async_log_success_event with a ModelResponse and completion_start_time so
the async time_to_first_token trim branch is actually exercised.
Previously no test touched that code path: the sync TTFT test used
log_success_event, and the async latency test passed a plain dict
response_obj without stream/completion_start_time, so TTFT was never
computed and the async trim was unreached. Verified load-bearing by
reverting only the async TTFT slice — the new test fails and all others
pass.
* format
* fix: remove redundant deep copy
set_model_list already does the deep copy at the beginning of the call.
* fix: remove unused model_list arguments
The `model_list` parameter was being passed to classes that did not use it.
* fix: reduce per-request memory and time from O(N×M) to O(N)
No need to create a whole array for a simple look up.
* add: missing test
* fix: remove unused parameter
