fix: avoid Anthropic tool-history requests without tools

[seilk]

What does this PR do?

Fixes Anthropic/LiteLLM proxies rejecting requests when message history contains tool calls but tools param is empty. Adds a dummy tool when:

• Model is Anthropic/Claude
• Message history has tool-call or tool-result
• No tools provided The dummy tool is excluded from activeTools so it won't be invoked. Fixes #8246 Relates to #2915

How did you verify your code works?

• bun run tsc --noEmit passes
• Tested with LiteLLM gateway: tool-history requests now succeed
• Existing tests unaffected (557 pass, 95 fail - same as baseline)