Self-hosted z3.sx translator, prove.sx prover, parser unicode, auto reader macros

- z3.sx: SX-to-SMT-LIB translator written in SX (359 lines), replaces Python translation logic
- prove.sx: SMT-LIB satisfiability checker in SX — proves all 91 primitives sat by construction
- Parser: support unicode characters (em-dash, accented letters) in symbols
- Auto-resolve reader macros: #name finds name-translate in component env, no Python registration
- Platform primitives: type-of, symbol-name, keyword-name, sx-parse registered in primitives.py
- Cond heuristic: predicates ending in ? recognized as Clojure-style tests
- Library loading: z3.sx loaded at startup with reload callbacks for hot-reload ordering
- reader_z3.py: rewritten as thin shell delegating to z3.sx
- Split monolithic .sx files: essays (22), plans (13), reactive-islands (6) into separate files

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

shared/sx/ref/primitives.sx

@@ -553,3 +553,30 @@
   :params (condition &rest message)
   :returns "boolean"
   :doc "Assert condition is truthy; raise error with message if not.")
+
+
+;; --------------------------------------------------------------------------
+;; Type introspection — platform primitives
+;; --------------------------------------------------------------------------
+
+(define-module :stdlib.types)
+
+(define-primitive "type-of"
+  :params (x)
+  :returns "string"
+  :doc "Return type name: number, string, boolean, nil, symbol, keyword, list, dict, lambda, component, island, macro.")
+
+(define-primitive "symbol-name"
+  :params (sym)
+  :returns "string"
+  :doc "Return the name string of a symbol.")
+
+(define-primitive "keyword-name"
+  :params (kw)
+  :returns "string"
+  :doc "Return the name string of a keyword.")
+
+(define-primitive "sx-parse"
+  :params (source)
+  :returns "list"
+  :doc "Parse SX source string into a list of AST expressions.")