Implementation of SEP-986: Specify Format for Tool Names (#551)

* feat: implement SEP-986 tool name validation and error reporting

Adds validation for MCP tool naming conventions as specified in SEP-986.
Ensures Rust SDK enforces standardized tool name formats, provides clear
errors for invalid names, and improves consistency across implementations.

Signed-off-by: tanish111 <tanishdesai37@gmail.com>

* fix(doctests): correct import paths in tool_name_validation

Update doctest examples to use the correct module path
rmcp::handler::server::tool_name_validation instead of
rmcp::model::tool_name_validation.

Signed-off-by: tanish111 <tanishdesai37@gmail.com>

* fix: only warn when warnings exist

Prevent empty warnings array from triggering warning output.

Signed-off-by: tanish111 <tanishdesai37@gmail.com>

* fix: remove internal check

Signed-off-by: tanish111 <tanishdesai37@gmail.com>

* refactor: remove doc comments from validation functions

Signed-off-by: tanish111 <tanishdesai37@gmail.com>

* refactor: remove doc comments from add_route functions

Signed-off-by: tanish111 <tanishdesai37@gmail.com>

* refactor: make tool name validation helpers private

Made ToolNameValidationResult and its functions and fields private.
Made validate_tool_name and issue_tool_name_warning private.

Signed-off-by: tanish111 <tanishdesai37@gmail.com>

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Signed-off-by: tanish111 <tanishdesai37@gmail.com>

crates/rmcp/src/handler/server.rs

@@ -9,6 +9,7 @@ pub mod prompt;
 mod resource;
 pub mod router;
 pub mod tool;
+pub mod tool_name_validation;
 pub mod wrapper;
 impl<H: ServerHandler> Service<RoleServer> for H {
     async fn handle_request(