Aser server-affinity component expansion + readline buffer fix

adapter-sx.sx: aser-expand-component expands :affinity :server components
inline during SX wire format serialization. Binds keyword args via
eval-expr, children via aser (handles HTML tags), then asers the body.

ocaml_bridge.py: 10MB readline buffer for large spec responses.
nav-data.sx: evaluator.sx filename fix.

Page rendering stays on Python _eval_slot for now — full OCaml rendering
needs the page shell IO (headers, CSRF, CSS) migrated to OCaml IO bridge.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

spec/evaluator.sx

@@ -2257,7 +2257,10 @@
             (env-bind! local "children" children))
           (make-cek-state (component-body f) local kont))
 
-      :else (error (str "Not callable: " (inspect f))))))
+      :else (error (str "Not callable: " (inspect f)
+                        (when raw-args
+                          (str " in (" (inspect (first raw-args)) " ...)")))))))
+
 
 
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