fix(tool_parser): support XML function_call and tool_call with invoke_name and parameters

[dpavlin]

Fixes #670

Summary

During multi-turn tool-calling sessions with DeepSeek-V4 (e.g., autonomous coding agents), the model may output tool calls wrapped in XML <function_call> or <tool_call> envelopes with <invoke_name> and <parameters> tags:

<function_call>
<invoke_name>read</invoke_name>
<parameters>
<path>/home/dpavlin/koha-rfid-go/internal/rfidops/ops.go</path>
</parameters>
</function_call>

Previously, Pattern 4b and Pattern 8 in tool_parser.cpp did not handle XML parameter blocks, leading to parse_tool_calls returning 0 calls, suppressing buffered tool text, and emitting an empty stop response to the client.

Changes

1. Added helper parse_xml_tool_call_body() in server/src/server/tool_parser.cpp:
   • Identifies tool name from <invoke_name>, <name>, <tool_name>, <function_name>, or <invoke name="...">.
   • Extracts parameters from <parameters> or <arguments> sections (supporting element tags <key>val</key> and attribute style <parameter name="key">val</parameter>).
   • Coerces parameter types based on declared tool schemas.
2. Hooked parse_xml_tool_call_body() into Pattern 4b (<function_call>) and Pattern 8 (<tool_call>).
3. Added comprehensive unit tests to server/test/test_server_unit.cpp covering single and multi-argument XML function/tool calls.

Verification

• test_server_unit: 426/426 passed.
• Verified on live DeepSeek-V4 Flash ROCm server with streaming SSE requests and agent workflows.

[cubic-dev-ai]

All reported issues were addressed across 2 files

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[cubic-dev-ai]

All reported issues were addressed across 2 files (changes from recent commits).

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