feat(sacp-cookbook): create dedicated cookbook crate with comprehensive examples

- Create sacp-cookbook crate with dependencies on sacp, sacp-conductor,
  sacp-rmcp, and sacp-tokio so all examples can compile as real doctests
- Add one_shot_prompt entry showing the simplest client pattern
- Simplify per_session_mcp_server to focus on on_proxy_session_start callback
- Add rmcp example to global_mcp_server (now compiles, was previously ignored)
- Update sacp cookbook.rs to redirect to sacp_cookbook crate
- Update sacp lib.rs to reference external cookbook crate

Author: nikomatsakis

Cargo.toml

@@ -2,6 +2,7 @@
 members = [
     "src/sacp-conductor",
     "src/sacp",
+    "src/sacp-cookbook",
     "src/sacp-derive",
     "src/sacp-tokio",
     "src/sacp-rmcp",

src/sacp-cookbook/Cargo.toml

@@ -0,0 +1,23 @@
+[package]
+name = "sacp-cookbook"
+version = "10.0.0-alpha.2"
+edition = "2024"
+description = "Cookbook of common patterns for building ACP components"
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/symposium-dev/symposium-acp"
+keywords = ["acp", "agent", "proxy", "mcp", "cookbook"]
+categories = ["development-tools"]
+
+[dependencies]
+sacp = { version = "10.0.0-alpha.2", path = "../sacp" }
+sacp-conductor = { version = "10.0.0-alpha.2", path = "../sacp-conductor" }
+sacp-rmcp = { version = "10.0.0-alpha.2", path = "../sacp-rmcp" }
+sacp-tokio = { version = "10.0.0-alpha.2", path = "../sacp-tokio" }
+
+# Re-export common dependencies needed by cookbook examples
+rmcp.workspace = true
+serde.workspace = true
+serde_json.workspace = true
+schemars.workspace = true
+tokio.workspace = true
+tracing.workspace = true