feat(compile): Phase 1 — wire shared persistent env (compile mode now works across forms)

Compile mode was broken: compiled defns interned only into the jolt namespace,
which Janet's eval couldn't see, so calling a compiled function threw 'unknown
symbol'. And load-string ignored :compile? entirely.

- Each context gets a persistent Janet env (ctx-janet-env), a child of the
  compiler module env (so core-* resolve) holding the context's user defs.
  compile-and-eval evals into it, so def/defn persist and resolve across forms;
  contexts stay isolated. nil ctx (one-off eval) gets a fresh child.
- Emit a named fn for defn ((def f (fn f [..] (f ..)))) so recursion resolves
  lexically (the anonymous form couldn't forward-reference f at compile time).
- Extract eval-one (per-form routing) and use it in both eval-string and
  load-string, so load-string honors :compile?. Stateful forms still interpret.

compiled fib(30): ~50s (interpreted) -> 3.4s (~15x). spec: compile-mode-test
gains cross-form/recursion/def + context-isolation cases. jpm test green.
Fast operator emission (the rest of the win) is Phase 2.

src/jolt/api.janet

@@ -43,6 +43,33 @@
     (install-async! ctx)
     ctx))
 
+# Stateful / context-modifying forms always use the interpreter (they mutate
+# the context: namespaces, macros, types, multimethods, dynamic vars, …).
+(defn- stateful-head? [head-name]
+  (or (= head-name "defmacro") (= head-name "ns")
+      (= head-name "deftype") (= head-name "defmulti") (= head-name "defmethod")
+      (= head-name "require") (= head-name "in-ns")
+      (= head-name "syntax-quote") (= head-name "set!")
+      (= head-name "var") (= head-name ".") (= head-name "new")
+      (= head-name "eval")))
+
+(defn eval-one
+  "Evaluate a single already-parsed form, routing to the compiler when the
+  context has :compile? enabled (stateful forms always interpret)."
+  [ctx form]
+  (if (get (ctx :env) :compile?)
+    (if (array? form)
+      (let [first-form (first form)
+            head-name (if (and (struct? first-form) (= :symbol (first-form :jolt/type)))
+                        (first-form :name) nil)]
+        (if (stateful-head? head-name)
+          (eval-form ctx @{} form)
+          (compile-and-eval form ctx)))
+      (if (or (and (struct? form) (= :symbol (form :jolt/type))) (tuple? form))
+        (compile-and-eval form ctx)
+        (eval-form ctx @{} form)))
+    (eval-form ctx @{} form)))
+
 (defn eval-string
   "Evaluate a Clojure source string in a Jolt context.
   When :compile? is enabled, compiles to Janet and evaluates.
@@ -50,31 +77,7 @@
   Context-modifying forms (ns, defmacro, deftype, require, in-ns, defmulti, defmethod)
   always use the interpreter."
   [ctx s]
-  (let [compile? (get (ctx :env) :compile?)
-        form (parse-string s)]
-    (if compile?
-      (if (array? form)
-        # Lists: check for stateful forms
-        (let [first-form (first form)
-              head-name (if (and (struct? first-form) (= :symbol (first-form :jolt/type)))
-                         (first-form :name)
-                         nil)
-              stateful? (or (= head-name "defmacro") (= head-name "ns")
-                            (= head-name "deftype") (= head-name "defmulti") (= head-name "defmethod")
-                            (= head-name "require") (= head-name "in-ns")
-                            (= head-name "syntax-quote") (= head-name "set!")
-                            (= head-name "var") (= head-name ".") (= head-name "new")
-                            (= head-name "eval"))]
-          (if stateful?
-            (eval-form ctx @{} form)
-            (compile-and-eval form ctx)))
-        # Bare symbols and other non-literal forms: also compile
-        (if (or (and (struct? form) (= :symbol (form :jolt/type)))
-                (tuple? form))
-          (compile-and-eval form ctx)
-          (eval-form ctx @{} form)))
-      # No compile flag: always interpret
-      (eval-form ctx @{} form))))
+  (eval-one ctx (parse-string s)))
 
 (defn eval-string*
   "Evaluate a Clojure source string with explicit bindings."
@@ -93,7 +96,7 @@
     (def [form rest] (parse-next cur))
     (set cur rest)
     (when (not (nil? form))
-      (set result (eval-form ctx @{} form))))
+      (set result (eval-one ctx form))))
   result)
 
 (defn compile-string

src/jolt/compiler.janet

@@ -8,6 +8,24 @@
 (use ./core)
 (use ./phm)
 
+# The compiler emits Janet that references the core fns (core-+, core-<, …),
+# which are bare-bound in this module's environment via (use ./core). Capture it
+# so each Jolt context can get a child env where those resolve and where compiled
+# `def`/`defn` bindings persist across forms (isolated per context).
+(def jolt-runtime-env (curenv))
+
+(defn ctx-janet-env
+  "Lazily create/cache a per-context Janet environment for compiled code: a child
+  of the runtime env (so core fns resolve) that holds this context's user defs.
+  For a nil context (one-off compile/eval) returns a fresh child env."
+  [ctx]
+  (if (and ctx (table? (get ctx :env)))
+    (or (get (ctx :env) :janet-rt)
+        (let [e (make-env jolt-runtime-env)]
+          (put (ctx :env) :janet-rt e)
+          e))
+    (make-env jolt-runtime-env)))
+
 (def- core-renames
   @{"+" "core-+"
     "-" "core-sub"
@@ -854,18 +872,30 @@
   (emit-expr (analyze-form form @{} ctx)))
 
 (defn compile-and-eval
-  "Compile a Clojure form and evaluate it as Janet.
-  For def/defn forms, interns the result in the Jolt namespace
-  so the interpreter can resolve it later."
+  "Compile a Clojure form and evaluate it as Janet, in the context's persistent
+  Janet env (so compiled def/defn bindings resolve across forms). For def/defn
+  forms, also interns the result in the Jolt namespace so the interpreter can
+  resolve it later."
   [form ctx]
-  (def result (eval (compile-ast form ctx)))
-  # Intern def/defn results in Jolt namespace for interpreter resolution
-  (when (and ctx (array? form) (> (length form) 0)
-             (struct? (first form)) (= :symbol ((first form) :jolt/type)))
-    (def head-name ((first form) :name))
-    (when (or (= head-name "def") (= head-name "defn") (= head-name "defn-"))
-      (def name-sym (in form 1))
-      (def name (if (struct? name-sym) (name-sym :name) name-sym))
-      (def ns (ctx-find-ns ctx (ctx-current-ns ctx)))
-      (ns-intern ns name result)))
+  (def env (ctx-janet-env ctx))
+  (def def-form? (and ctx (array? form) (> (length form) 0)
+                      (struct? (first form)) (= :symbol ((first form) :jolt/type))
+                      (let [h ((first form) :name)] (or (= h "def") (= h "defn") (= h "defn-")))))
+  (def def-name (when def-form?
+                  (let [name-sym (in form 1)] (if (struct? name-sym) (name-sym :name) name-sym))))
+  (var compiled (compile-ast form ctx))
+  # Name the fn after the def so a recursive body self-references lexically
+  # ((def f (fn [..] (f ..))) -> (def f (fn f [..] (f ..)))); the anonymous form
+  # can't resolve f at compile time.
+  (when (and def-name (indexed? compiled) (= 3 (length compiled))
+             (= 'def (in compiled 0))
+             (indexed? (in compiled 2)) (= 'fn (in (in compiled 2) 0))
+             (indexed? (in (in compiled 2) 1)))   # 3rd elem is (fn [params] ...)
+    (let [f (in compiled 2)]
+      (set compiled [(in compiled 0) (in compiled 1)
+                     [(in f 0) (symbol def-name) ;(tuple/slice f 1)]])))
+  (def result (eval compiled env))
+  # Also intern def/defn results in the Jolt namespace for interpreter resolution.
+  (when def-name
+    (ns-intern (ctx-find-ns ctx (ctx-current-ns ctx)) def-name result))
   result)