compute: remove the correction v1 buffer

[antiguru]

The enable_compute_correction_v2 flag has served true in production for every build at or beyond 26.7.0-rc.1, so the v1 correction buffer is dead code in every deployment we support. This removes it along with the flag that selected between the two implementations.

CorrectionV2 becomes the only Correction, and its file moves to sink/correction.rs. The logging and metrics helpers that both implementations shared move to sink/correction/logging.rs, which keeps the buffer file from growing further. Correction::new now reads the chain proportionality and chunk size from the ConfigSet, matching the constructor the sink previously called on the enum wrapper; Correction::with_params takes the two values directly for tests and benchmarks.

Removing v1 also removes its only consumer of ConsolidatingVec, so that type and the consolidating_vec_growth_dampener dyncfg that tuned it are gone as well. Both flag keys move to the LaunchDarkly consistency check's stale list, because the last published release still synchronizes them. The flags themselves still need archiving in LaunchDarkly.

The equivalence_with_v1 unit test compared the two implementations step by step. It is replaced by equivalence_with_reference, which runs the same upsert-and-feedback workload against a naive in-test buffer that keeps every update in a flat vector, plus an assertion that each step emits something so the comparison cannot pass vacuously. The correction benchmark loses its version-dispatch wrapper and now measures the single implementation.

The dyncfg keys compute_correction_v2_chain_proportionality and compute_correction_v2_chunk_size keep their names. Renaming them would drop the production overrides currently set against those keys.

doc/developer/generated/ still documents correction_v2 and the removed dyncfgs. That tree is regenerated by the documentation agent, so it is untouched here.

Release notes

This release will not change any user-visible behavior.

🤖 Generated with Claude Code