Improve web search region selection and normalize provider resultsHEADmain

Update ddgs to 9.16.0 and keep backend="auto" while preserving the
LLM-facing query/max_results inputs and title/href/body result schema.

Implementation:
- Add OLLAMA_WEB_SEARCH_REGION with auto/us-en/jp-jp values, normalized
  configuration input, and a clear startup error for unsupported values.
- In auto mode, detect kana after NFKC normalization and exclusion of URLs
  and site:/filetype: tokens. Select jp-jp for kana and us-en otherwise,
  without modifying the original query or sharing per-call region state.
- Preserve href/url and body/snippet fallbacks and normalize None values.
- Reject malformed HTTP(S) URLs without DNS lookups or extra requests.
- Unwrap known Yahoo redirect URLs before excluding Bing aclick ads.
- Represent missing and URL-only titles as empty strings rather than
  inventing titles from snippets. Preserve remaining provider order and
  allow fewer results after filtering, without additional searches.
- Preserve provider exception propagation and identify ddgs in error logs.

Coverage and documentation:
- Add 72 regression cases for configuration, region routing, concurrency,
  public schemas, title/URL/ad boundaries, limits, and search_and_fetch
  continuation. Update existing provider mocks and log assertions.
- Document the region environment setting and result semantics in both
  READMEs and tools-schema.md; update the changelog.
- Keep only a short backend availability caveat in tools-schema.md and
  remove the temporary backend comparison, design, and validation docs.

Validation:
- pytest: 222 passed; ruff check . and mypy src/ passed.
- uv lock --check and git diff --check passed.
- Initial live acceptance: 56 searches plus 3 registry smoke checks;
  default-region auto succeeded 8/18 times and real ad filtering removed
  two ads. Stable relevance/title quality targets remain unmet because
  provider acquisition is unreliable.
- Follow-up backend study: 234 comparative searches plus 3 Yahoo response
  diagnostics. Yahoo led individual backends at 9/18; restricted multi-
  backend combinations did not outperform the contemporaneous auto
  control. Authentication, access restrictions, temporary upstream
  failures, and Yahoo HTML/parser mismatches were observed.

Do not claim search reliability is fixed or add backend configuration,
custom retries, ranking changes, or challenge bypasses. Running app
processes were not restarted; restart is needed to load the changes.

1 files changed, 6 insertions, 4 deletions

diff --git a/tests/test_tools.py b/tests/test_tools.py
index 6ba537b..487ce98 100644
--- a/tests/test_tools.py
+++ b/tests/test_tools.py
@@ -103,7 +103,9 @@ def test_web_search_mocked():
         def __exit__(self, *a):
             return None
 
-        def text(self, q, max_results=5):
+        def text(self, q, max_results=5, *, region, backend):
+            assert region == "us-en"
+            assert backend == "auto"
             return fake
 
     monkey = MagicMock()
@@ -126,7 +128,7 @@ def test_web_search_returns_empty_list_for_no_provider_results() -> None:
         def __exit__(self, *args):
             return None
 
-        def text(self, query, max_results=5):
+        def text(self, query, max_results=5, *, region, backend):
             return []
 
     with patch.object(search_mod, "DDGS", EmptyDDGS):
@@ -145,7 +147,7 @@ def test_web_search_logs_and_propagates_provider_errors(
         def __exit__(self, *args):
             return None
 
-        def text(self, query, max_results=5):
+        def text(self, query, max_results=5, *, region, backend):
             raise RuntimeError("403 Forbidden")
 
     with (
@@ -155,7 +157,7 @@ def test_web_search_logs_and_propagates_provider_errors(
         with pytest.raises(RuntimeError, match="403 Forbidden"):
             search_mod.web_search("private search terms")
 
-    assert "DuckDuckGo web search failed" in caplog.text
+    assert "ddgs web search failed" in caplog.text
     assert "private search terms" not in caplog.text
 
     registry = ToolRegistry()