[AZ-839] Fix C3 fixture path mismatch (batch 108b)

The batch 108 fixture built tile_store + descriptor_index from
the static operator config (root_dir baked into YAML) but built
the AC-3/AC-6 verifier from cache_root/descriptor.index (fresh
tmp path). On Tier-2 the descriptor_batcher would write under
the YAML root and the verifier would open the tmp path, raising
IndexUnavailableError before the fixture could yield a
PopulatedC6Cache. Unit tests missed it because every test
stubbed descriptor_index_factory.

Mutate the c6_tile_cache config block in-memory at fixture entry
so root_dir = cache_root and faiss_index_path falls back to
<cache_root>/descriptor.index. Production C6 components and the
verifier now share one path source. Align tile_store_path with
PostgresFilesystemStore's <root_dir>/tiles layout so the
integration test's tile_store_path.is_dir() assertion holds.

Driver and unit tests are path-agnostic and unaffected. Batch
108b report documents the defect, the fix, and the self-review
miss.

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/e2e/replay/conftest.py

@@ -15,6 +15,7 @@ import shutil
 import subprocess
 import sys
 from collections.abc import Iterator
+import dataclasses
 from dataclasses import dataclass
 from pathlib import Path
 from typing import Any
@@ -430,8 +431,26 @@ def _build_operator_pre_flight_cache(
     config = load_config(os.environ, paths=[config_path])
 
     cache_root = tmp_path_factory.mktemp("operator_pre_flight_cache")
-    tile_store_path = cache_root / "tile_store"
-    tile_store_path.mkdir(parents=True, exist_ok=True)
+    # PostgresFilesystemStore writes JPEGs under `<root_dir>/tiles/`;
+    # FaissDescriptorIndex falls back to `<root_dir>/descriptor.index`
+    # when `faiss_index_path` is empty. Override the c6_tile_cache
+    # block in-memory so the production components built below
+    # (build_tile_store / build_descriptor_index / batcher) write to
+    # the same `cache_root` PopulatedC6Cache advertises. Without this
+    # the static YAML at GPS_DENIED_OPERATOR_CONFIG_PATH would route
+    # writes to its baked-in `root_dir` while the verifier read from
+    # the fixture's tmp path, breaking AC-3 / AC-6 on Tier-2.
+    c6_block = config.components["c6_tile_cache"]
+    c6_block_overridden = dataclasses.replace(
+        c6_block,
+        root_dir=str(cache_root),
+        faiss_index_path="",
+    )
+    config = dataclasses.replace(
+        config,
+        components={**config.components, "c6_tile_cache": c6_block_overridden},
+    )
+    tile_store_path = cache_root / "tiles"
     faiss_index_path = cache_root / "descriptor.index"
 
     route_spec = extract_route_from_tlog(