Implement reader macros (#;, #|...|, #', #name) and #z3 demo

Reader macros in parser.sx spec, Python parser.py, and hand-written sx.js:
- #; datum comment: read and discard next expression
- #|...|  raw string: no escape processing
- #' quote shorthand: (quote expr)
- #name extensible dispatch: registered handler transforms next expression

#z3 reader macro demo (reader_z3.py): translates define-primitive
declarations from primitives.sx into SMT-LIB verification conditions.
Same source, two interpretations — bootstrappers compile to executable
code, #z3 extracts proof obligations.

48 parser tests (SX spec + Python), all passing. Rebootstrapped JS+Python.
Demo page at /plans/reader-macro-demo with side-by-side examples.

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

shared/sx/ref/sx_ref.py

@@ -1,5 +1,3 @@
-# WARNING: special-forms.sx declares forms not in eval.sx: reset, shift
-# WARNING: eval.sx dispatches forms not in special-forms.sx: form?
 """
 sx_ref.py -- Generated from reference SX evaluator specification.
 
@@ -990,7 +988,7 @@ sf_named_let = lambda args, env: (lambda loop_name: (lambda bindings: (lambda bo
 )[-1]), bindings) if sx_truthy(((type_of(first(bindings)) == 'list') if not sx_truthy((type_of(first(bindings)) == 'list')) else (len(first(bindings)) == 2))) else reduce(lambda acc, pair_idx: _sx_begin(_sx_append(params, (symbol_name(nth(bindings, (pair_idx * 2))) if sx_truthy((type_of(nth(bindings, (pair_idx * 2))) == 'symbol')) else nth(bindings, (pair_idx * 2)))), _sx_append(inits, nth(bindings, ((pair_idx * 2) + 1)))), NIL, range(0, (len(bindings) / 2)))), (lambda loop_body: (lambda loop_fn: _sx_begin(_sx_set_attr(loop_fn, 'name', loop_name), _sx_dict_set(lambda_closure(loop_fn), loop_name, loop_fn), (lambda init_vals: call_lambda(loop_fn, init_vals, env))(map(lambda e: trampoline(eval_expr(e, env)), inits))))(make_lambda(params, loop_body, env)))((first(body) if sx_truthy((len(body) == 1)) else cons(make_symbol('begin'), body)))))([]))([]))(slice(args, 2)))(nth(args, 1)))(symbol_name(first(args)))
 
 # sf-lambda
-sf_lambda = lambda args, env: (lambda params_expr: (lambda body: (lambda param_names: make_lambda(param_names, body, env))(map(lambda p: (symbol_name(p) if sx_truthy((type_of(p) == 'symbol')) else p), params_expr)))(nth(args, 1)))(first(args))
+sf_lambda = lambda args, env: (lambda params_expr: (lambda body_exprs: (lambda body: (lambda param_names: make_lambda(param_names, body, env))(map(lambda p: (symbol_name(p) if sx_truthy((type_of(p) == 'symbol')) else p), params_expr)))((first(body_exprs) if sx_truthy((len(body_exprs) == 1)) else cons(make_symbol('begin'), body_exprs))))(rest(args)))(first(args))
 
 # sf-define
 sf_define = lambda args, env: (lambda name_sym: (lambda value: _sx_begin((_sx_set_attr(value, 'name', symbol_name(name_sym)) if sx_truthy((is_lambda(value) if not sx_truthy(is_lambda(value)) else is_nil(lambda_name(value)))) else NIL), _sx_dict_set(env, symbol_name(name_sym), value), value))(trampoline(eval_expr(nth(args, 1), env))))(first(args))
@@ -1424,6 +1422,9 @@ on_event = lambda el, event_name, handler: dom_listen(el, event_name, handler)
 # bridge-event
 bridge_event = lambda el, event_name, target_signal, transform_fn: effect(lambda : (lambda remove: remove)(dom_listen(el, event_name, lambda e: (lambda detail: (lambda new_val: reset_b(target_signal, new_val))((invoke(transform_fn, detail) if sx_truthy(transform_fn) else detail)))(event_detail(e)))))
 
+# resource
+resource = lambda fetch_fn: (lambda state: _sx_begin(promise_then(invoke(fetch_fn), lambda data: reset_b(state, {'loading': False, 'data': data, 'error': NIL}), lambda err: reset_b(state, {'loading': False, 'data': NIL, 'error': err})), state))(signal({'loading': True, 'data': NIL, 'error': NIL}))
+
 
 # =========================================================================
 # Fixups -- wire up render adapter dispatch
@@ -1486,4 +1487,4 @@ def render(expr, env=None):
 
 def make_env(**kwargs):
     """Create an environment dict with initial bindings."""
-    return dict(kwargs)
+    return dict(kwargs)