fix(serve): parse tool calls with empty/omitted argument markers in ToolParser

[Ultron09]

Summary

When Kimi / DeepSeek models generate parameterless tool calls or tool calls without explicit arguments (e.g. <|tool_call_begin|>functions.get_time:0<|tool_call_end|>), or when a streaming reply terminates while in the header state before <|tool_call_argument_begin|>, ToolParser previously bypassed _parse_header() because header parsing was only triggered upon receiving _ARG_BEGIN.

As a result, any tool call lacking an argument block was silently discarded from self.calls when _CALL_END or _SECTION_END arrived.

Changes

1. serve/kimitools.py:
   • In ToolParser.feed_marker(): Check if self._state == "header" when receiving _CALL_END or _SECTION_END, parse the header into a ToolCall, append to self.calls, and finalize arguments (json_block).
   • In ToolParser.finish(): If the stream terminates while in "header" state, flush and parse the pending header into self.calls.
2. serve/engine.py:
   • In version() and build_info(): Catch EngineError when libwaste shared library is unbuilt so server health endpoints and test runners degrade gracefully.
3. tests/serve/test_chatfmt.py:
   • Added unit tests:
     • test_kimi_tool_call_without_arguments_marker
     • test_kimi_tool_call_stream_ended_in_header

Verification

• Ran python -m unittest tests.serve.test_chatfmt (51/51 tests pass).
• Ran all 244 serve tests via python -m unittest discover -s tests/serve -t . -p "test_*.py" (244/244 OK).

[mfethe1]

Validated on macOS 15.6 / arm64 against head cce7c67.

Full suite on PR head: python3 -m pytest tests/serve/test_chatfmt.py -q → 51 passed (main's 49 + the 2 new).

Must-bite control: reverted only serve/ to main (c66c7b3), kept the new tests → the 2 new tests FAIL on unpatched code (test_kimi_tool_call_without_arguments_marker, test_kimi_tool_call_stream_ended_in_header) while all 49 pre-existing still pass. The tests genuinely pin the fix, not the fixture.

Edge probes on PR head (beyond the author's tests):

• Two no-arg calls back-to-back → [('get_time',0,''), ('ping',1,'')] — no duplication, indexes correct.
• section_end while in header state after a prior complete call → no double-append of the earlier call (the self._current is not None guard ordering is right).
• Non-int index suffix (functions.get_time:abc) → name parsed, index falls back to positional 0 — pre-existing _parse_header semantics preserved.

Nit (non-blocking): <|tool_call_begin|> immediately followed by <|tool_call_end|> (empty header) now emits a call with name='' rather than dropping it silently. Arguably correct (the model did emit a call marker), but worth a one-line decision; OpenAI-compat consumers may prefer arguments: {}. Not a merge blocker for me.

engine.py note: the version()/build_info() EngineError → "unknown"/"unbuilt" change is behavior-preserving for built engines; it converts a hard-fail into a sentinel for unbuilt engines — consistent with how run.sh distinguishes engine-missing from engine-wrong. No regression observed.

Verdict: approve — minimal three-site state-machine patch (_CALL_END, _SECTION_END, finish()), tests bite on unpatched code, no regression in the surrounding 49.