Sync& mcp tool callback addmethod

[paoxiaomooo]

Add filtered constructors for MCP Tool Callback Providers

This PR introduces new constructors for both SyncMcpToolCallbackProvider and AsyncMcpToolCallbackProvider to allow initialization with a filtered subset of MCP clients based on allowed server names.

Changes

• Added a constructor to SyncMcpToolCallbackProvider that:

  • Accepts a full list of McpSyncClient instances and a set of allowed server names
  • Filters clients to only include those with names in the allowed list
  • Applies no additional tool-level filtering

• Added a similar constructor to AsyncMcpToolCallbackProvider for McpAsyncClient

• Ensured that both constructors validate non-null and non-empty input parameters

Motivation

When building large-scale AI workflows, users may want to initialize tool callback providers with only a subset of trusted or registered MCP servers. These new constructors provide a convenient way to restrict tool resolution to specific servers without affecting existing usage.

Compatibility

These additions are non-breaking and fully backward-compatible. Default constructors remain unchanged.

Why Add Server Filtering?

1. Selective Tool Discovery – Only fetch tools from specified servers, reducing overhead and improving performance.
2. Consistent API – Matches the sync version’s functionality, avoiding surprises.
3. Reactive Efficiency – Built-in non-blocking filtering for cleaner, optimized async flows.
4. Operational Control – Enables precise server management in multi-server environments.

Before: Manual filtering + duplicate checks.
After: Single-line reactive filtering with validation.
// Cleaner, safer usage
Flux tools = asyncToolCallbacksByServer(clients, allowedServers);