feat: Add prompt support (#351)

* feat: add prompt support with typed argument handling

- Implement #[prompt], #[prompt_router], and #[prompt_handler] macros
- Add automatic JSON schema generation from Rust types for arguments
- Support flexible async handler signatures with automatic adaptation
- Create PromptRouter for efficient prompt dispatch
- Include comprehensive tests and example implementation

This enables MCP servers to provide reusable prompt templates that
LLMs can discover and invoke with strongly-typed parameters, similar
to the existing tool system but optimized for prompt use cases.

🤖 Generated with Claude Code
Co-Authored-By: Claude <noreply@anthropic.com>

* refactor: unify parameter handling between tools and prompts

- Replace Arguments<T> with Parameters<T> for consistent API
- Create shared common module for tool/prompt utilities
- Modernize async handling with futures::future::BoxFuture
- Move cached_schema_for_type to common module for reuse
- Update error types from rmcp::Error to rmcp::ErrorData
- Add comprehensive trait implementations for parameter extraction

🤖 Generated with Claude Code

Co-Authored-By: Claude <noreply@anthropic.com>

* refactor: extract Parameters wrapper to shared module and unify trait usage

- Move Parameters type from common.rs to dedicated wrapper/parameters.rs module
- Unify extractor traits by using FromContextPart for both tools and prompts
- Remove duplicate FromToolCallContextPart and FromPromptContextPart traits
- Add structured output support to Json wrapper with IntoCallToolResult impl
- Improve error messages with more descriptive panic for schema serialization
- Update all imports across codebase to use new module path
- Clean up trailing whitespace and formatting inconsistencies

This consolidates parameter extraction logic and reduces code duplication
between tool and prompt handlers while maintaining backward compatibility.

* chore: remove committed .egg-info directory and update gitignore

* docs: fix documentation formatting

examples/transport/src/common/calculator.rs

@@ -2,7 +2,10 @@
 
 use rmcp::{
     ServerHandler,
-    handler::server::{router::tool::ToolRouter, tool::Parameters, wrapper::Json},
+    handler::server::{
+        router::tool::ToolRouter,
+        wrapper::{Json, Parameters},
+    },
     model::{ServerCapabilities, ServerInfo},
     schemars, tool, tool_handler, tool_router,
 };
@@ -27,14 +30,16 @@ pub struct Calculator {
     tool_router: ToolRouter<Self>,
 }
 
-#[tool_router]
 impl Calculator {
     pub fn new() -> Self {
         Self {
             tool_router: Self::tool_router(),
         }
     }
+}
 
+#[tool_router]
+impl Calculator {
     #[tool(description = "Calculate the sum of two numbers")]
     fn sum(&self, Parameters(SumRequest { a, b }): Parameters<SumRequest>) -> String {
         (a + b).to_string()