feat(rmcp): separate model and wire tool names

[mikemikimike]

Fixes #2232

Summary

• Add RmcpToolRegistration with separate model_name and MCP wire definition.name.
• Preserve existing rmcp_tool(s) and timeout behavior when the names are identical.
• Expose alias-aware registration through ToolServer and both AgentBuilder tool states.
• Keep provider/toolset lookup on the model name while sending the original MCP name in tools/call.
• Add deterministic in-process MCP regression tests for aliases and duplicate wire names across servers.

Validation

• cargo test -p rig-agent --features rmcp — 500 passed, 2 ignored
• cargo clippy -p rig-agent --features rmcp --all-targets --all-features -- -D warnings
• cargo fmt --all -- --check
• cargo check -p rig-agent --no-default-features
• git diff --check