test(e2e): register the poller batch cost join as its own uncovered cell

The retrieve writer and the CheckBatchCost poller are two different spend
writers, and the in-run failed batch only proves the first. Split the
key_attribution batch cell in two: retrieve_batch_cost_joins_retrieving_key,
which test_terminal_batch_cost_row_joins_the_retrieving_key claims, and
poller_batch_cost_joins_creating_key, which no test claims yet and so shows
up on the coverage dashboard as a P1 gap instead of hiding behind the
retrieve leg. The rationale records why one run cannot hand the poller a
completed batch on a stack that boots a fresh Postgres per build.

tests/e2e/CLAUDE.md

@@ -188,7 +188,8 @@ quota_management.<behavior>.<variant>.<assertion>
               | routes_to_fallback | reseed_matches_db | reports_spend | logs_cost | zero_cost
               | matches_sum_of_logs | loses_no_spend | attributes_spend | writes_own_rows
               | writes_failure_row | returns_cost | keeps_total | joins_key | reports_alias_and_email
-              | health_rows_keep_service_account | batch_cost_joins_key
+              | health_rows_keep_service_account | retrieve_batch_cost_joins_retrieving_key
+              | poller_batch_cost_joins_creating_key
   e.g.  quota_management.ratelimit.rpm.blocks_over_limit           exercised_on=[chat_completions, messages]
         quota_management.budget.key.blocks_over_limit              exercised_on=[chat_completions]
 ```

tests/e2e/coverage_registry/quota_management.yaml

@@ -61,4 +61,5 @@
 - {id: quota_management.spend_tracking.key_attribution.joins_key, module: quota_management, tier: P1, behavior: spend_tracking, variant: key_attribution, assertions: [joins_key], exercised_on: [chat_completions, messages, responses, embeddings, batches, files, google_native, rust_control_plane], source: "proxy/spend_tracking/spend_tracking_utils.py", rationale: "Every spend row a virtual key writes across chat, queued chat, messages, responses, embeddings, the Gemini passthrough, file upload, batch create, and a replayed callback log carries api_key equal to the key's token hash and the key alias, the join the usage APIs depend on; a re-hashed token shows up as an unattributed key-hash-* row (#39568, #39572)"}
 - {id: quota_management.spend_tracking.key_attribution.reports_alias_and_email, module: quota_management, tier: P1, behavior: spend_tracking, variant: key_attribution, assertions: [reports_alias_and_email], exercised_on: [chat_completions, messages, responses, embeddings, batches, files, google_native, rust_control_plane], source: "proxy/management_endpoints/internal_user_endpoints.py", rationale: "/spend/logs?api_key= returns every one of the key's rows with its alias and /user/daily/activity aggregates them under the key's token with key_alias and user_email; /spend/logs carries no email field, so the email is asserted on daily activity only"}
 - {id: quota_management.spend_tracking.key_attribution.health_rows_keep_service_account, module: quota_management, tier: P1, behavior: spend_tracking, variant: key_attribution, assertions: [health_rows_keep_service_account], exercised_on: [chat_completions], source: "proxy/health_check.py", rationale: "A /health probe's spend row stays keyed by the literal litellm-internal-health-check service account rather than a hash of it, so health spend never appears as an unattributed key"}
-- {id: quota_management.spend_tracking.key_attribution.batch_cost_joins_key, module: quota_management, tier: P1, behavior: spend_tracking, variant: key_attribution, assertions: [batch_cost_joins_key], exercised_on: [batches], source: "proxy/batches_endpoints/endpoints.py", rationale: "The retrieve that first sees a batch in a terminal state writes its {provider_batch_id}_batch_cost row, so the batch each run creates is one OpenAI fails at validation within seconds and the test retrieves it by its raw provider id with the same key until it is failed; that raw-id retrieve is never owned by the CheckBatchCost poller, so it prices the batch inline against the retrieving key and the row must carry that key's token hash and alias. A completed batch with a positive cost is out of one run's reach: OpenAI's completion window is 24h and a stack booted fresh per run lists no earlier run's batches"}
+- {id: quota_management.spend_tracking.key_attribution.retrieve_batch_cost_joins_retrieving_key, module: quota_management, tier: P1, behavior: spend_tracking, variant: key_attribution, assertions: [retrieve_batch_cost_joins_retrieving_key], exercised_on: [batches], source: "proxy/batches_endpoints/endpoints.py", rationale: "The retrieve that first sees a batch in a terminal state prices it inline and writes its {provider_batch_id}_batch_cost row against the retrieving key, so the batch each run creates is one OpenAI fails at validation within seconds and the test retrieves it by its raw provider id with the same key until it is failed; a raw id is never owned by the CheckBatchCost poller, and the row must carry that key's token hash and alias"}
+- {id: quota_management.spend_tracking.key_attribution.poller_batch_cost_joins_creating_key, module: quota_management, tier: P1, behavior: spend_tracking, variant: key_attribution, assertions: [poller_batch_cost_joins_creating_key], exercised_on: [batches], source: "enterprise/litellm_enterprise/proxy/common_utils/check_batch_cost.py", rationale: "The CheckBatchCost poller bills a completed, positive-cost batch created through a unified id against the key that created it, a different writer from the inline retrieve. No test claims this cell yet: OpenAI's completion window is 24h and both e2e stacks boot a fresh Postgres per build, so a completed batch is out of one run's reach and the managed list never shows an earlier run's batch; the cell stays visible as a gap until a run can hand a completed batch to the poller"}

tests/e2e/quota_management/spend_tracking/test_key_attribution_e2e.py

@@ -283,9 +283,7 @@ class TestKeyAttribution:
     )
     def test_every_write_path_row_joins_the_key(self, client: SpendClient, driven: DrivenKey) -> None:
         assert tuple(path.name for path in driven.paths) == WRITE_PATHS
-        found: Final = tuple(
-            (path, client.proxy.poll_logs_for_request_id(path.request_id)) for path in driven.paths
-        )
+        found: Final = tuple((path, client.proxy.poll_logs_for_request_id(path.request_id)) for path in driven.paths)
         unwritten: Final = [path.name for path, rows in found if not rows]
         assert not unwritten, f"write paths that produced no spend row within the poll window: {unwritten}"
         unjoined: Final = [
@@ -379,7 +377,7 @@ class TestKeyAttribution:
         assert not rehashed, f"health-check rows keyed by something other than {HEALTH_SERVICE_ACCOUNT!r}: {rehashed}"
 
     @pytest.mark.covers(
-        "quota_management.spend_tracking.key_attribution.batch_cost_joins_key",
+        "quota_management.spend_tracking.key_attribution.retrieve_batch_cost_joins_retrieving_key",
         exercised_on=["batches"],
     )
     def test_terminal_batch_cost_row_joins_the_retrieving_key(self, client: SpendClient, driven: DrivenKey) -> None: