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, 11 insertions, 0 deletions

diff --git a/README_ja.md b/README_ja.md
index ccb8a39..088ac73 100644
--- a/README_ja.md
+++ b/README_ja.md
@@ -79,6 +79,17 @@ ollama-web
 | `OLLAMA_WEB_MCP_STDIO_ALLOWLIST` | 未設定 | stdio MCP で起動を許可する実行ファイル絶対パスのカンマ区切り |
 | `OLLAMA_WEB_MCP_HTTPS_ALLOWLIST` | 未設定 | remote HTTPS MCP 接続を許可するホスト名のカンマ区切り |
 | `OLLAMA_WEB_LANGUAGE` | `ja` | UI と LLM プロンプトの表示言語（`ja` または `en`） |
+| `OLLAMA_WEB_SEARCH_REGION` | `auto` | 検索地域。`auto` / `us-en` / `jp-jp`。auto はかなを含むクエリを日本、それ以外を米国として検索 |
+
+検索は ddgs の `backend="auto"` を使用します。地域は内部で選び、LLM に公開する引数は
+`query` と `max_results` のままです。判定では半角カナも正規化し、URL と `site:` / `filetype:`
+のトークンを除外します。検索へ送る元クエリは変更しません。漢字だけのクエリは `us-en`
+になるため、日本へ固定する場合は `jp-jp` を設定してください。UI 言語には連動せず、
+設定変更の反映にはアプリの再起動が必要です。不正な設定値では起動時にエラーになります。
+
+構文上無効な URL と既知の Bing 広告リンクを除外し、空・URL 形式のタイトルは空文字にして
+URL と要約を保持します。除外で件数が減っても追加検索は行いません。provider の失敗は
+ツールエラーとして伝えます。
 
 ### 多言語対応