test: comprehensive V2 unit tests for tools, vision, knowledge, providers

[DeepRatAI]

Summary

Adds 144 new unit tests across 4 new test files covering all major V2 modules. Replaces the broken V1 test_tools.py (25/33 failed) with a fully V2-aligned test_tools_v2.py.

Changes

New Test Files

File	Tests	Module Covered
test_tools_v2.py	63	ToolParameter, ToolDefinition, ToolCall, ToolResult, ToolError, ToolRegistry, ToolExecutor, medical tools (drug interactions, dosage, labs, emergency), enums
test_vision.py	16	ImageAnalyzer (validation, extensions, size limits), ImagingModality enum, ImageValidation dataclass
test_knowledge.py	31	MedicalCondition, Medication, DiagnosticProcedure, ClinicalProtocol, MedicalKnowledgeBase, DrugMonograph, DrugInteraction, InteractionSeverity, RouteOfAdministration, PharmaceuticalDatabase
test_providers.py	34	ProviderConfig (API key resolution), ProviderResponse (success property), ProviderStatus enum, ModelProvider (status management, error classification), ProviderManager

Removed

• tests/test_tools.py — broken V1 test file with 25/33 failures due to API mismatches (replaced by test_tools_v2.py)

CI Updates

• Required tests: 4 → 8 files (test_tools_v2, test_vision, test_knowledge, test_providers added)
• Extended tests: new files added to ignore list (avoids double-running)
• Total required test count: 136 existing + 144 new = 280 tests

Testing

• All 144 new tests pass locally on Python 3.12
• Lint clean (ruff + black)
• All 136 existing required tests unaffected

Closes #1

Gonzalo