fix(read-lifecycle): harden CCR persistence (is None + import guard + try/except)

Address Copilot review feedback:

- content_router.py: explicit `is None` check (truthiness override would
  discard falsy test doubles); guard the `get_compression_store` import so
  a stripped build without the module still runs read_lifecycle, matching
  smart_crusher's pattern.
- read_lifecycle.py: wrap `store.store(...)` in try/except with a
  precomputed fallback hash so a transient backend failure can't break
  compress(), mirroring read_maturation.py.

22 tests pass; end-to-end via headroom.compress() still hits the store.

headroom/transforms/content_router.py

@@ -2417,12 +2417,22 @@ class ContentRouter(Transform):
         """
         # Pre-process: Read lifecycle management (stale/superseded detection)
         if self.config.read_lifecycle.enabled:
-            from ..cache.compression_store import get_compression_store
             from .read_lifecycle import ReadLifecycleManager
 
+            # is None (not truthiness) so falsy test doubles are honored;
+            # guarded import keeps read_lifecycle running in stripped builds.
+            injected_store = kwargs.get("compression_store")
+            if injected_store is None:
+                try:
+                    from ..cache.compression_store import get_compression_store
+
+                    injected_store = get_compression_store()
+                except ImportError:
+                    pass
+
             lifecycle_mgr = ReadLifecycleManager(
                 self.config.read_lifecycle,
-                compression_store=kwargs.get("compression_store") or get_compression_store(),
+                compression_store=injected_store,
             )
             lifecycle_result = lifecycle_mgr.apply(
                 messages,

headroom/transforms/read_lifecycle.py

@@ -474,21 +474,24 @@ class ReadLifecycleManager:
         if content_bytes < self.config.min_size_bytes:
             return False, content, None
 
-        # Store original in CCR if available
-        ccr_hash = None
+        # Best-effort CCR persistence (mirrors read_maturation.py): a store
+        # failure must not break compress().
+        ccr_hash = hashlib.sha256(content.encode()).hexdigest()[:24]
         if self.store is not None:
-            ccr_hash = self.store.store(
-                original=content,
-                compressed="",
-                tool_name="Read",
-                tool_call_id=classification.tool_call_id,
-                compression_strategy=f"read_lifecycle:{classification.state.value}",
-            )
-
-        # Generate marker
-        if ccr_hash is None:
-            # No CCR store — generate a content hash for reference
-            ccr_hash = hashlib.sha256(content.encode()).hexdigest()[:24]
+            try:
+                ccr_hash = self.store.store(
+                    original=content,
+                    compressed="",
+                    tool_name="Read",
+                    tool_call_id=classification.tool_call_id,
+                    compression_strategy=f"read_lifecycle:{classification.state.value}",
+                )
+            except Exception as e:  # noqa: BLE001 - storage failure must not break the request
+                logger.warning(
+                    "read_lifecycle: CCR store failed for %s: %s",
+                    classification.tool_call_id,
+                    e,
+                )
 
         file_display = classification.file_path or "unknown"