test(read-lifecycle): add ContentRouter regression test; pass explicit_hash

Address Copilot review (round 2):

- tests/test_transforms/test_read_lifecycle.py: new integration test that
  drives the fix through headroom.compress() and asserts the STALE Read
  marker's hash resolves in the global CCR store (tool=Read,
  strategy=read_lifecycle:stale). Guards against the original bug
  regressing.
- headroom/transforms/read_lifecycle.py: pass explicit_hash=ccr_hash to
  store.store() so the precomputed fallback hash is reused (no double
  SHA-256) and the marker/store key stays consistent if the store's
  default hash ever changes.

23 tests pass (was 22).

headroom/transforms/read_lifecycle.py

@@ -485,6 +485,7 @@ class ReadLifecycleManager:
                     tool_name="Read",
                     tool_call_id=classification.tool_call_id,
                     compression_strategy=f"read_lifecycle:{classification.state.value}",
+                    explicit_hash=ccr_hash,
                 )
             except Exception as e:  # noqa: BLE001 - storage failure must not break the request
                 logger.warning(

tests/test_transforms/test_read_lifecycle.py

@@ -610,3 +610,88 @@ class TestNoFilePathHandling:
         # Can't match file_path, so Read is not classified at all
         assert result.reads_total == 0
         assert result.messages[1]["content"] == LARGE_CONTENT
+
+
+class TestContentRouterIntegration:
+    """Regression: ContentRouter.transform must wire a real CCR store into
+    ReadLifecycleManager so STALE Read markers resolve via headroom_retrieve."""
+
+    def test_stale_read_marker_retrievable_via_compress(self, monkeypatch):
+        import re
+
+        # Force an in-memory backend so the test is hermetic.
+        monkeypatch.setenv("HEADROOM_CCR_BACKEND", "memory")
+
+        from headroom import compress
+        from headroom.cache.compression_store import (
+            get_compression_store,
+            reset_compression_store,
+        )
+
+        reset_compression_store()
+
+        large_content = "source line\n" * 500  # above read_lifecycle min_size_bytes
+        messages = [
+            {
+                "role": "assistant",
+                "content": [
+                    {
+                        "type": "tool_use",
+                        "id": "t1",
+                        "name": "Read",
+                        "input": {"file_path": "/tmp/foo.txt"},
+                    }
+                ],
+            },
+            {
+                "role": "user",
+                "content": [
+                    {
+                        "type": "tool_result",
+                        "tool_use_id": "t1",
+                        "content": large_content,
+                    }
+                ],
+            },
+            # Edit the same file -> the Read above becomes STALE.
+            {
+                "role": "assistant",
+                "content": [
+                    {
+                        "type": "tool_use",
+                        "id": "t2",
+                        "name": "Edit",
+                        "input": {"file_path": "/tmp/foo.txt"},
+                    }
+                ],
+            },
+            {
+                "role": "user",
+                "content": [
+                    {
+                        "type": "tool_result",
+                        "tool_use_id": "t2",
+                        "content": "edited",
+                    }
+                ],
+            },
+        ]
+
+        result = compress(messages, model="claude-sonnet-4-5-20250929")
+
+        hashes: list[str] = []
+        for m in result.messages:
+            content = m.get("content")
+            if isinstance(content, list):
+                for b in content:
+                    if isinstance(b, dict) and b.get("type") == "tool_result":
+                        s = b.get("content", "")
+                        if isinstance(s, str):
+                            hashes.extend(re.findall(r"hash=([a-f0-9]+)", s))
+        assert hashes, "Expected a STALE Read marker with a hash"
+
+        store = get_compression_store()
+        entry = store.retrieve(hashes[0])
+        assert entry is not None, "STALE Read marker hash not in CCR store"
+        assert entry.tool_name == "Read"
+        assert entry.compression_strategy == "read_lifecycle:stale"