model: append tool outputschema to tool description

[Flash-LHR]

The openai/anthropic SDK don’t expose an output-schema field for tools, so we surface the schema in descriptions to give the LLM stronger guidance on tool return shapes.

[codecov]

Codecov Report

❌ Patch coverage is 72.72727% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 87.30476%. Comparing base (2c3e558) to head (b4e87dc).
⚠️ Report is 6 commits behind head on main.

Files with missing lines	Patch %	Lines
model/anthropic/anthropic.go	72.72727%	2 Missing and 1 partial ⚠️
model/openai/openai.go	72.72727%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@                 Coverage Diff                 @@
##                main        #756         +/-   ##
===================================================
- Coverage   87.33385%   87.30476%   -0.02909%     
===================================================
  Files            277         277                 
  Lines          35962       35982         +20     
===================================================
+ Hits           31407       31414          +7     
- Misses          2980        2988          +8     
- Partials        1575        1580          +5     

Flag	Coverage Δ
unittests	87.30476% <72.72727%> (-0.02909%)	⬇️

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[WineChord]

LGTM