* test(integration): add read-replica routing harness
* refactor(integration): hoist the maintenance url imports
* fix(integration): keep per-test databases and the witness sequence readable under replica roles
* fix(integration): opt bespoke database and pool tests out of the injected read replica
* test(integration): commit recorded replica routing expectations
* fix(integration): judge routing by role containment so shrinking role sets do not fail
* fix(integration): run the pool-limit shutdown choreography on the superuser database url
* ci(integration): add the mcp group to the replica matrix
* fix(integration): judge routing by exact role sets with a named either-role allowlist
* test(integration): drop containment-era routing expectations for re-recording
* chore(integration): drop docstrings from the replica harness scripts
* docs(integration): describe exact routing matching and the either-role list
* test(integration): record exact replica routing expectations
* test(integration): allow the SELECT 1 health probe on either role
* test(integration): replace committed routing expectations with an on-demand base-vs-head parity run
* test(integration): fix parity env scope, readme wording, and seed-deterministic serialization test
* test(integration): make the sorted-role serialization test deterministic in-process
* test(integration): swap all product code in parity runs and pin role gains
* ci(integration): force tracked-file removal before parity checkout
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Co-authored-by: yuneng <yuneng@berri.ai>
