feat: Add compact AST dump

Introduce a new `dump_ast_compact` function for the environment and
Dumper. This function provides a simplified, human-readable
representation of the AST, focusing on inferred types and purity markers
instead of detailed debug information.

This change adds:
- A `compact` flag to the `Dumper` struct.
- The `dump_compact` method to the `Dumper`.
- The `dump_ast_compact` method to the `Environment`.
- A new `dump_ast_compact` command-line argument for the `ast` binary.
- A new MCP server endpoint `dump_ast_compact`.
- A `CompactMetadata` trait to abstract over different metadata types
  for compact display.
- Updates to documentation and CLI help messages.

src/ast/mcp_server.rs

@@ -70,10 +70,12 @@ impl MycMcpServer {
         }
     }
 
-    /// Dumps the compiled and optimized AST for a Myc expression.
+    /// Dumps the compiled and optimized AST for a Myc expression (verbose debug format).
     #[tool(description = "Compile a Myc expression and return a human-readable dump of \
         the compiled AST. Useful for understanding how the compiler transforms code \
-        through its optimization and lowering passes.")]
+        through its optimization and lowering passes. \
+        Returns the full debug format including binding addresses and stack offsets. \
+        Use dump_ast_compact for a cleaner view focused on types and purity.")]
     fn dump_ast(&self, Parameters(CodeInput { code }): Parameters<CodeInput>) -> String {
         let env = Self::make_env();
         match env.dump_ast(&code) {
@@ -82,6 +84,20 @@ impl MycMcpServer {
         }
     }
 
+    /// Dumps the compiled AST in compact, human-readable format.
+    #[tool(description = "Compile a Myc expression and return a compact AST dump showing \
+        inferred types (e.g. 'fn([int]) -> bool') and purity markers ('!' for impure, \
+        '~' for side-effect-free). '[tail]' marks tail-call positions. \
+        Omits internal details like stack offsets and binding addresses. \
+        Prefer this over dump_ast when you want to understand the type structure of an expression.")]
+    fn dump_ast_compact(&self, Parameters(CodeInput { code }): Parameters<CodeInput>) -> String {
+        let env = Self::make_env();
+        match env.dump_ast_compact(&code) {
+            Ok(dump) => dump,
+            Err(e) => format!("Error: {}", e),
+        }
+    }
+
     /// Checks the syntax and types of a Myc expression without executing it.
     #[tool(description = "Check the syntax and types of a Myc expression without running it. \
         Returns 'OK' if the code is valid, or a list of compiler diagnostics on error. \