* feat(search): add DeepSeek as a /v1/search provider
Adds DeepSeekSearchConfig for POST https://api.deepseek.com/v1/tools/search, registers it under search_provider=deepseek, prices deepseek/search at 0.00075 per query and marks search support in provider_endpoints_support.json
* fix(search): reject DeepSeek queries over the 128 character limit before the call
* test(search): escape regex metacharacters in DeepSeek query limit match
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Co-authored-by: devin-ai-integration[bot] <158243242+devin-ai-integration[bot]@users.noreply.github.com>
