Specialize record field reads in method bodies; fix with-meta on symbols (#141)

A protocol method reads its fields through the generic guarded keyword lookup
because the method's `this` param is untyped. defrecord now hints `this` with
the record type, the per-form inference seeds ^Record-hinted params (the
:fn branch previously typed all params :any — only the whole-program path
seeded phints), and run-passes feeds the inference the record shapes. So a
hinted param's field reads bare-index instead of going through the :jolt/type
tag guard.

This needed a with-meta fix: (with-meta sym ..) returned a proto'd table, so
symbol? was false and the macro-attached hint broke fn destructuring. Symbols
now carry metadata in-place in their struct (matching how the reader attaches
^hint), keeping symbol? true, as in Clojure.

Modest on dispatch (~3-5%): the field read is a small fraction of a dispatch;
the machinery (record-tag + protocol lookup + wrapper) dominates, which is the
inline-cache target (jolt-ez5h). But it's a correctness fix and lets any
^Record-hinted code — not just methods — drop the field-read guard per-form,
not only under whole-program.

Co-authored-by: Yogthos <yogthos@gmail.com>

src/jolt/core_extra.janet

@@ -55,9 +55,17 @@
 (defn core-with-meta [obj meta]
   # Functions and scalars can't carry metadata in Jolt's model — return as-is
   # rather than crashing (Clojure attaches meta only to IObj values).
-  (if (or (function? obj) (cfunction? obj) (number? obj) (boolean? obj)
-          (nil? obj) (string? obj) (keyword? obj) (buffer? obj))
+  (cond
+    (or (function? obj) (cfunction? obj) (number? obj) (boolean? obj)
+        (nil? obj) (string? obj) (keyword? obj) (buffer? obj))
     obj
+    # Symbols carry metadata IN-PLACE in their struct's :meta field (this is how
+    # the reader attaches ^hint and keeps symbol? true — see reader/read-meta).
+    # The table-proto path below would make (symbol? (with-meta sym ..)) false and
+    # break destructuring/hint reading, so keep a symbol a symbol.
+    (and (struct? obj) (= :symbol (obj :jolt/type)))
+    (struct ;(kvs obj) :meta meta)
+    true
     (do
       (var new-obj @{})
       (each k (keys obj)