* feat(ci): rebalance test shards from recorded timings
* fix(ci): preserve artifact retries for shard timings
Find shard-plan generation by its stable step ID and clarify the native runner cohort count (#3748).
Note: pre-existing reference-oracle parser type failures in two test_oracle_assets cases remain outside this change.
* fix(ci): keep retry timing snapshots immutable
Require the existing snapshot on reruns so a failed download cannot refresh history and change shard assignments. Cover the workflow contract and document recovery when the artifact is unavailable.
* docs(ci): document shard timing profile selection
* fix(ci): balance cold shard estimates consistently
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Co-authored-by: Gergo Magyar <gergomagyar0@gmail.com>
