chore: deduplicate src/search modules (cache, content, query) into shims (#2506)

* chore: dedupe src/search/cache.py into a re-export shim

src/search/cache.py was a byte-identical copy of services/search/cache.py.
Convert it to a sys.modules alias of the canonical services module (matching
src/search/core.py, providers.py, ranking.py) so the two cannot drift, and add
an identity assertion to test_search_module_consolidation.py.

content.py and query.py are intentionally left as-is: the copies have drifted
and services lacks fixes that src has, so they need services reconciled first
before they can be shimmed safely.

* chore: dedupe src/search content.py and query.py into shims

Convert src/search/content.py and query.py to sys.modules aliases of the
canonical services/search/* (matching cache.py, core.py, providers.py,
ranking.py) so the duplicate copies cannot drift.

Repoint the two tests that were coupled to the src-copy internals onto the
canonical services surface (behaviour is equivalent):
- test_src_search_query_nonstring.py: import services.search.query instead of
  loading the src file by path.
- test_security_regressions.py::test_web_fetch_guard_blocks_redirect_into_private:
  mock httpx.get (services uses the module-level get, not httpx.Client) and
  assert on the canonical 'Blocked' message.

Drop the now-redundant [src_content, service_content] parametrization in
test_search_content_extraction_parity.py and test_search_content_url_guards.py
(after the shim both params are the same object); add content/query identity
assertions to test_search_module_consolidation.py.

tests/test_src_search_query_nonstring.py

@@ -1,22 +1,12 @@
-import importlib.machinery
-import importlib.util
-from pathlib import Path
+"""Query helpers must tolerate non-string input.
+
+`src.search.query` is a compatibility shim that aliases the canonical
+`services.search.query`, so this exercises the live implementation.
+"""
+import services.search.query as q
 
 
-_PATH = Path(__file__).resolve().parents[1] / "src" / "search" / "query.py"
-
-
-def _load():
-    loader = importlib.machinery.SourceFileLoader("odysseus_src_search_query", str(_PATH))
-    spec = importlib.util.spec_from_loader(loader.name, loader)
-    module = importlib.util.module_from_spec(spec)
-    loader.exec_module(module)
-    return module
-
-
-def test_src_search_helpers_handle_non_string_queries():
-    q = _load()
-
+def test_query_helpers_handle_non_string_queries():
     assert q._detect_question_type(None) is None
     assert q._split_multi_part(None) == []
     assert q._extract_site_filter(None) == ("", None)
@@ -25,9 +15,7 @@ def test_src_search_helpers_handle_non_string_queries():
     assert isinstance(q.build_enhanced_query(123), str)
 
 
-def test_src_search_valid_query_still_works():
-    q = _load()
-
+def test_query_valid_query_still_works():
     assert q._detect_question_type("who is bob") == "who"
     assert q._is_news_query("latest news today") is True
     assert q._extract_site_filter("cats site:x.com")[1] == "x.com"