revert: drop release_hosts signature change + scaffolding (belongs to #287)

The release_hosts provider_data-optional change and the ProviderHandlerBase
scaffolding protocol overlap with PR #287 (provider onboarding prep), which
owns the cross-provider handler contract and rewrites these same handler
files. That work does not belong in this k8s perf/parity PR.

Reverts the handler signature changes to main and removes the orphaned
scaffolding file (which was an incomplete copy of #287's — missing __init__
and siblings). The contract-test adapter is restored to main's
captured-provider_data pattern. The kmock list-semantics fix is unaffected
and retained.

Author: fgogolli

src/orb/providers/base/scaffolding/handler_base.py

@@ -555,7 +555,7 @@ def check_hosts_status(self, request: Request) -> CheckHostsStatusResult:
     async def release_hosts(
         self,
         machine_ids: list[str],
-        provider_data: Optional[dict[str, Any]] = None,
+        provider_data: dict[str, Any],
     ) -> None:
         """Delete the pods/workloads identified by ``machine_ids``.
 
@@ -565,12 +565,6 @@ async def release_hosts(
         so the handler can resolve context without needing the full Request
         aggregate.  The dict is the same object that was stamped under
         ``Request.provider_data`` by ``acquire_hosts``.
-
-        ``provider_data`` defaults to ``None``; concrete handlers treat a
-        missing dict the same as ``{}`` and fall back to configured defaults
-        (e.g. the handler's default namespace).  This makes the signature
-        compatible with the base ``ProviderHandlerBase`` contract, which
-        calls ``release_hosts(machine_ids)`` without provider-specific context.
         """
 
     @classmethod

src/orb/providers/k8s/infrastructure/handlers/base_handler.py

@@ -232,7 +232,7 @@ def check_hosts_status(self, request: Request) -> CheckHostsStatusResult:
     async def release_hosts(
         self,
         machine_ids: list[str],
-        provider_data: Optional[dict[str, Any]] = None,
+        provider_data: dict[str, Any],
     ) -> None:
         """Selective or full release using pod-deletion-cost + replicas patch.
 
@@ -254,10 +254,8 @@ async def release_hosts(
             provider_data: The ``provider_data`` dict stamped onto the
                 Request aggregate at acquire time.  Carries ``namespace``
                 and ``deployment_name`` (falls back to deterministic
-                defaults when absent).  Defaults to ``None``; treated as
-                ``{}`` internally.
+                defaults when absent).
         """
-        provider_data = provider_data or {}
         request_id = provider_data.get("request_id", "unknown")
         if not machine_ids:
             self._logger.debug(

src/orb/providers/k8s/infrastructure/handlers/deployment_handler.py

@@ -196,7 +196,7 @@ def check_hosts_status(self, request: Request) -> CheckHostsStatusResult:
     async def release_hosts(
         self,
         machine_ids: list[str],
-        provider_data: Optional[dict[str, Any]] = None,
+        provider_data: dict[str, Any],
     ) -> None:
         """Delete the whole Job (cascade-deletes pods).
 
@@ -214,14 +214,12 @@ async def release_hosts(
                 ``provider_data["parallelism"]``); a subset is rejected.
             provider_data: The ``provider_data`` dict stamped onto the
                 Request aggregate at acquire time.  Carries ``namespace``,
-                ``job_name`` and ``parallelism``.  Defaults to ``None``;
-                treated as ``{}`` internally.
+                ``job_name`` and ``parallelism``.
 
         Raises:
             K8sError: When ``machine_ids`` covers fewer pods than the
                 Job was created with.
         """
-        provider_data = provider_data or {}
         request_id = provider_data.get("request_id", "unknown")
         if not machine_ids:
             self._logger.debug(

src/orb/providers/k8s/infrastructure/handlers/job_handler.py

@@ -285,7 +285,7 @@ def check_hosts_status(self, request: Request) -> CheckHostsStatusResult:
     async def release_hosts(
         self,
         machine_ids: list[str],
-        provider_data: Optional[dict[str, Any]] = None,
+        provider_data: dict[str, Any],
     ) -> dict[str, Any]:
         """Delete the named pods concurrently; 404s are best-effort.
 
@@ -306,9 +306,8 @@ async def release_hosts(
             provider_data: The ``provider_data`` dict stamped onto the
                 Request aggregate at acquire time.  Carries
                 ``namespace`` (falls back to the provider default when
-                absent).  Defaults to ``None``; treated as ``{}`` internally.
+                absent).
         """
-        provider_data = provider_data or {}
         request_id = provider_data.get("request_id", "unknown")
         if not machine_ids:
             self._logger.debug(

src/orb/providers/k8s/infrastructure/handlers/pod_handler.py

@@ -217,7 +217,7 @@ def check_hosts_status(self, request: Request) -> CheckHostsStatusResult:
     async def release_hosts(
         self,
         machine_ids: list[str],
-        provider_data: Optional[dict[str, Any]] = None,
+        provider_data: dict[str, Any],
     ) -> None:
         """Selective or full release using ordinal-aware scale-down.
 
@@ -253,10 +253,8 @@ async def release_hosts(
             provider_data: The ``provider_data`` dict stamped onto the
                 Request aggregate at acquire time.  Carries ``namespace``
                 and ``statefulset_name`` (falls back to deterministic
-                defaults when absent).  Defaults to ``None``; treated as
-                ``{}`` internally.
+                defaults when absent).
         """
-        provider_data = provider_data or {}
         request_id = provider_data.get("request_id", "unknown")
         if not machine_ids:
             self._logger.debug(