v0.19.1

This is a patch release on top of v0.19.0 with Transformers v5.5.3 upgrade and bug fixes for Gemma4:

• Update to transformers v5 (#30566)
• [Bugfix] Fix invalid JSON in Gemma 4 streaming tool calls by stripping partial delimiters (#38992)
• [Bugfix][Frontend] Fix Gemma4 streaming HTML duplication after tool calls (#38909)
• [Bugfix] Fix Gemma4 streaming tool call corruption for split boolean/number values (#39114)
• [Tool] adjust_request to reasoning parser, and Gemma4 fixes (#39027)
• [Gemma4] Support quantized MoE (#39045)
• Add Gemma4 Eagle3 support (#39450)
• [Gemma4][Bugfix]: Enable Gemma4ForCasualLM to load lora adapters correctly (#38844)
• [Bugfix] Fix Gemma4 tool parser converting bare null to string "null" (#39679)
• [Model] Fix Gemma 4 token repetition by dynamic BOS injection for PT models (#39842)
• fix(kimi_k25): resolve media_placeholder_token_id from tokenizer (#39344)