refactor(v2): isolate legacy provider stack and prune obsolete tests

README.md

@@ -22,7 +22,8 @@ Runtime services are intentionally small:
 - optional `scheduler` profile service (runs daily extractor/import loop)
 
 No Redis/Celery services are part of the v2 default runtime topology.
-Legacy Celery/provider code is still in repository history/codebase but de-emphasized for v2.
+Legacy Celery/provider code remains in-repo but is isolated behind `LEGACY_PROVIDER_STACK_ENABLED=1`.
+Default v2 runtime keeps that stack disabled.
 
 ## Image Strategy
 
@@ -96,6 +97,7 @@ Core groups:
 - snapshot directory vars (`STATIC_DATASET_*`)
 - optional future scheduler vars (`SCHEDULER_*`)
 - daily orchestration vars (`DAILY_ORCHESTRATION_*`)
+- optional legacy provider-sync toggle (`LEGACY_PROVIDER_STACK_ENABLED`)
 
 ## Snapshot Storage Convention
 
@@ -404,3 +406,7 @@ This v2 work branch is:
 
 Legacy provider/Celery ingestion layers are not the default runtime path for v2 foundation.
 They are intentionally isolated until replaced by v2 snapshot ingestion commands in later tasks.
+By default:
+- `apps.providers` is not installed
+- `/providers/` routes are not mounted
+- legacy provider-specific settings are not required