Add pipe operator, with-update, retry/fallback, reason, parallel, trace, contract, deploy

Implements 8 new language features:
- |> pipe operator: a |> f desugars to f(a), left-associative chains
- with record update: let b = a with { field: val } — non-destructive struct update
- retry/fallback: retry N times { ... } fallback { ... } with counter-based loop codegen
- reason: AI inference primitive calling soma /v1/chat/completions at runtime
- parallel: concurrent execution block returning a Map of named results via threads
- trace: zero-cost observability block emitting TraceBegin/TraceEnd with ms timing
- requires: precondition annotation on fn, emits ContractCheck bytecode at entry
- deploy: deployment-as-syntax posting to soma /v1/deploy at runtime

All features thread through lexer → parser/AST → codegen → runtime interpreter.

crates/el-parser/src/ast.rs

@@ -126,6 +126,24 @@ pub enum Expr {
         fields: Vec<(String, Expr)>,
         span: Span,
     },
+    /// Record update: `a with { field: new_val }`
+    With {
+        base: Box<Expr>,
+        updates: Vec<(String, Expr)>,
+    },
+    /// AI inference: `reason "query"`
+    Reason {
+        query: String,
+    },
+    /// Concurrent execution: `parallel { name: expr, ... }`
+    Parallel {
+        entries: Vec<(String, Expr)>,
+    },
+    /// Trace block: `trace "label" { stmts }`
+    Trace {
+        label: String,
+        body: Vec<Stmt>,
+    },
 }
 
 // ── Match arm ─────────────────────────────────────────────────────────────────
@@ -198,7 +216,7 @@ pub enum Stmt {
     Return(Expr, Span),
     /// A bare expression used as a statement (usually a call).
     Expr(Expr, Span),
-    /// `fn name<T, E>(params) -> ReturnType { body }` (with optional decorators)
+    /// `fn name<T, E>(params) -> ReturnType [requires cond] { body }` (with optional decorators)
     FnDef {
         name: String,
         decorators: Vec<Decorator>,
@@ -206,6 +224,8 @@ pub enum Stmt {
         type_params: Vec<String>,
         params: Vec<Param>,
         return_type: TypeExpr,
+        /// Optional precondition: `requires expr`
+        requires: Option<Box<Expr>>,
         body: Vec<Stmt>,
         span: Span,
     },
@@ -252,6 +272,20 @@ pub enum Stmt {
         methods: Vec<Stmt>,
         span: Span,
     },
+    /// `retry N times { ... } fallback { ... }`
+    Retry {
+        count: Expr,
+        body: Vec<Stmt>,
+        fallback: Option<Vec<Stmt>>,
+        span: Span,
+    },
+    /// `deploy fn_name to "/route" via target`
+    Deploy {
+        fn_name: String,
+        route: String,
+        target: String,
+        span: Span,
+    },
 }
 
 // ── Top-level program ─────────────────────────────────────────────────────────