Tool mappers silently drop unsupported WebSearch config fields

[Kamilbenkirane]

Priority: High
Related: #199
Replaces: #223

All tool mappers silently drop WebSearch config fields the underlying API doesn't support. No warning, no error — the user thinks they're filtering domains but nothing happens.

Current behavior per provider:

Provider	allowed_domains	blocked_domains	max_uses
Anthropic	mapped	mapped	mapped
Google	dropped	mapped (as exclude_domains)	dropped
OpenResponses/OpenAI	mapped (as filters.allowed_domains)	dropped	dropped
Groq	dropped	dropped	dropped
Moonshot	dropped	dropped	dropped

Fix: Emit UnsupportedParameterWarning (not an error) when a non-None WebSearch field is dropped.

This follows celeste's existing pattern from PR #212 — warn and drop, don't error. Celeste is a primitive SDK (like Anthropic SDK, OpenAI SDK), not a framework. Primitives don't gatekeep — they normalize what they can and warn when something is lost. Users who want strict behavior can promote via warnings.filterwarnings("error", category=UnsupportedParameterWarning).

Example warning message:

WebSearch.blocked_domains is not supported by OpenResponses and will be ignored.
If this is now supported, please file an issue. Workaround: use a raw dict tool
(e.g. tools=[{"type": "web_search", "filters": {"blocked_domains": [...]}}]).

Files:

• src/celeste/protocols/openresponses/tools.py (WebSearchMapper — warn on blocked_domains, max_uses)
• src/celeste/providers/google/generate_content/tools.py (WebSearchMapper — warn on allowed_domains, max_uses)
• src/celeste/providers/groq/chat/tools.py (WebSearchMapper — warn on all 3)
• src/celeste/providers/moonshot/chat/tools.py (WebSearchMapper — warn on all 3)