fix(agent): report unknown tool parameters

[yanpgwang]

Summary

• validate top-level tool input keys against explicitly declared parameters
• report an unknown parameter together with a missing required parameter
• preserve open input semantics for dynamic map[string]T tools and tools without a declared schema
• sort unknown parameter names for deterministic errors
• add focused coverage for fixed, dynamic, missing, and unknown parameter combinations

This makes errors such as old-string versus old_string explicit so models can correct malformed tool calls without rejecting legitimate dynamic tool inputs.

Tests

• go test ./... -count=1 -timeout=30m
• go vet ./...
• golangci-lint run

Fixes #304