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, 8 insertions, 0 deletions

diff --git a/src/ollama_web/config.py b/src/ollama_web/config.py
index fa07384..484038a 100644
--- a/src/ollama_web/config.py
+++ b/src/ollama_web/config.py
@@ -12,6 +12,13 @@ def _csv_env(name: str) -> list[str]:
     return [part.strip() for part in raw.split(",") if part.strip()]
 
 
+def _search_region_env() -> str:
+    region = os.environ.get("OLLAMA_WEB_SEARCH_REGION", "auto").strip().lower()
+    if region not in {"auto", "us-en", "jp-jp"}:
+        raise ValueError("OLLAMA_WEB_SEARCH_REGION must be one of: auto, us-en, jp-jp")
+    return region
+
+
 @dataclass
 class Settings:
     """Runtime settings resolved from environment variables."""
@@ -48,6 +55,7 @@ class Settings:
     scrape_timeout: float = 15.0
     scrape_max_chars: int = 4000
     search_max_results: int = 5
+    search_region: str = field(default_factory=_search_region_env)
     fetch_max_results: int = 3
     fetch_max_chars: int = 8000
     max_fetch_mb: int = 10