chat: remove fallback parsers, update tests to use proper parser initialization
- Remove fallback parser code from chat-parser.cpp - tests should always
initialize parsers with tools (no more "fallback" concept)
- Update GLM 4.5 tests to properly initialize parser with tools and
reasoning_format, fixing interleaved thinking extraction
- Update Kimi K2 tests to use proper parser initialization with tools
- Update Qwen3 Coder XML tests with comprehensive tool definitions
including proper types and required fields
- Fix constructed_mapper to trim whitespace from string values using
string_strip() before JSON serialization
- Make Qwen3 Coder XML parser flexible with optional whitespace
All formats now follow the principle: "always have a parser" - tests
properly initialize parsers with tool schemas for full validation.
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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>