fix(retrieval): use stock Ministral embedding backbone (#3103)

* fix(retrieval): use stock Ministral embedding backbone

Signed-off-by: Oliver Holworthy <1216955+oliverholworthy@users.noreply.github.com>

* fix(retrieval): preserve Ministral loading contracts

Signed-off-by: Oliver Holworthy <1216955+oliverholworthy@users.noreply.github.com>

* fix(retrieval): preserve legacy Hub authentication

Signed-off-by: Oliver Holworthy <1216955+oliverholworthy@users.noreply.github.com>

* refactor(retrieval): scope extracted config overrides

Signed-off-by: Oliver Holworthy <1216955+oliverholworthy@users.noreply.github.com>

* fix(retrieval): preserve standard Ministral score dispatch

Signed-off-by: Oliver Holworthy <1216955+oliverholworthy@users.noreply.github.com>

* fix(retrieval): preserve native loader kwargs

Signed-off-by: Oliver Holworthy <1216955+oliverholworthy@users.noreply.github.com>

* refactor(retrieval): inline extracted config cloning

Signed-off-by: Oliver Holworthy <1216955+oliverholworthy@users.noreply.github.com>

* refactor(retrieval): remove transient source revision

Signed-off-by: Oliver Holworthy <1216955+oliverholworthy@users.noreply.github.com>

* refactor(retrieval): tighten stock Ministral scope

Signed-off-by: Oliver Holworthy <1216955+oliverholworthy@users.noreply.github.com>

* test(retrieval): drop obsolete auth kwarg expectation

Signed-off-by: Oliver Holworthy <1216955+oliverholworthy@users.noreply.github.com>

* fix(retrieval): keep embedding metadata outside backbone

Signed-off-by: Oliver Holworthy <1216955+oliverholworthy@users.noreply.github.com>

* fix(retrieval): make embedding fallbacks bidirectional

Signed-off-by: Oliver Holworthy <1216955+oliverholworthy@users.noreply.github.com>

* refactor(retrieval): restore config override layout

Signed-off-by: Oliver Holworthy <1216955+oliverholworthy@users.noreply.github.com>

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Signed-off-by: Oliver Holworthy <1216955+oliverholworthy@users.noreply.github.com>