fix(tools): validate Brave search parameters

[rubenssoto]

Summary

• expose Brave localization parameters only when the active search provider is Brave, with provider-supported enums in the tool schema
• normalize country, search language, UI language, and freshness values before constructing the Brave request; unsupported markets fall back to ALL
• infer zh-hans or zh-hant from supported Chinese country/UI regions when callers provide the generic zh language
• keep cached Brave results separated by normalized localization, freshness, and Accept-Language context
• retry an HTTP 422 once without optional Brave filters so a stale or rejected localization value does not abort the search
• cover the complete Brave HTTP retry flow with a mock server, including request sanitization, header preservation, retry selection, and retry-response errors

Validation

Completed

• cargo fmt --all -- --check
• git diff --check
• ./scripts/check-file-size.sh
• cargo test --locked -p moltis-tools --all-features web_search -- --nocapture (43 passed)
• cargo clippy --locked -p moltis-tools --all-features --all-targets -- -D warnings
• ./scripts/local-validate.sh 1245 at a035d594 (partial: fmt, Biome, TypeScript, i18n, zizmor, install checks, file-size, lockfile, and web assets passed)
• full release Docker image build at a035d594; the cache/Chinese normalization follow-up was validated with targeted tests and clippy

Remaining

• remaining workspace-wide local validation — attempted locally; the lint build is blocked by this host's native toolchain while compiling the unrelated llama-cpp-sys-2 dependency
• CI

Manual QA

• built and deployed moltis-local:20260824.01-obscura-v021-brave-pr1245; the gateway started normally and /health returned HTTP 200
• sent the formerly failing Paraguay/Spanish combination as the sanitized request generated by the implementation (country=ALL, search_lang=es, invalid ui_lang omitted, freshness=pw) from the running container; Brave returned HTTP 200 with three results
• mocked HTTP coverage verifies the first request, one filter-free retry after 422, preserved authentication/localization headers, successful response parsing, no retry when no optional filters exist, and propagation of a failed retry response

[greptile-apps]

Greptile Summary

The PR validates and normalizes Brave-specific search parameters while improving retry behavior and cache separation.

• Exposes provider-supported localization parameters only for Brave.
• Normalizes localization, freshness, and Chinese script variants before request construction.
• Retries rejected optional filters once without those filters.
• Separates cached results by normalized Brave parameters and Accept-Language.
• Adds mock HTTP coverage for successful and failed retry paths.

Confidence Score: 5/5

The PR appears safe to merge.

No blocking failure remains within the scope of this follow-up review, and the previously requested retry-path coverage is present at the current head.

Important Files Changed

Filename	Overview
crates/tools/src/web_search.rs	Integrates normalized Brave parameters into schema generation, request execution, cache keys, and fully mocked retry-path tests.
crates/tools/src/web_search/brave.rs	Adds provider-local enum definitions and normalization logic for Brave localization and freshness parameters.

_{Reviews (2): Last reviewed commit: "fix(tools): preserve Brave search contex..." | Re-trigger Greptile}

[rubenssoto]

Addressed two additional correctness cases in 7ad57b78:

• Brave cache keys now include the normalized country, search language, UI language, freshness, and Accept-Language, preventing localized/freshness variants of the same query from reusing mismatched cached results.
• Generic zh now resolves to zh-hans for CN and zh-hant for HK/TW, using the supported country/UI locale context.

Added regression coverage for normalized cache-key equivalence/separation and both Chinese scripts. Validation passes: 43 targeted web_search tests, clippy with all features/all targets and -D warnings, fmt, diff check, and file-size check.

@greptile-apps please re-review the updated head.