feat: Anthropic web server tools, provider metadata, messaging hardening

- Add local web_search/web_fetch SSE handling and optional tool schemas
- Extend HeuristicToolParser for JSON-style WebFetch/WebSearch text
- Consolidate provider defaults, ids, and exception typing; stream contracts
- Messaging: typed options, voice config injection, platform contract cleanup
- Tests for web server tools, converters, parsers, contracts; ignore debug-*.log

providers/defaults.py

@@ -0,0 +1,19 @@
+"""Default upstream base URLs and shared provider constants.
+
+Adapters and :mod:`providers.registry` import from here to avoid duplicating
+literals and to keep ``providers.registry`` free of per-adapter eager imports.
+"""
+
+# OpenAI-compatible chat (NIM, DeepSeek) and local OpenAI-shaped endpoints
+NVIDIA_NIM_DEFAULT_BASE = "https://integrate.api.nvidia.com/v1"
+DEEPSEEK_DEFAULT_BASE = "https://api.deepseek.com"
+OPENROUTER_DEFAULT_BASE = "https://openrouter.ai/api/v1"
+LMSTUDIO_DEFAULT_BASE = "http://localhost:1234/v1"
+LLAMACPP_DEFAULT_BASE = "http://localhost:8080/v1"
+
+# Backward-compatible names used by existing adapter modules
+NVIDIA_NIM_BASE_URL = NVIDIA_NIM_DEFAULT_BASE
+DEEPSEEK_BASE_URL = DEEPSEEK_DEFAULT_BASE
+OPENROUTER_BASE_URL = OPENROUTER_DEFAULT_BASE
+LMSTUDIO_DEFAULT_BASE_URL = LMSTUDIO_DEFAULT_BASE
+LLAMACPP_DEFAULT_BASE_URL = LLAMACPP_DEFAULT_BASE