docs: clarify fn*/let*/loop* take plain symbols only (jolt-f79)

grammar.ebnf: the destructuring note already attributed patterns to the
binding MACROS; make the boundary explicit — the fn*/let*/loop* PRIMITIVES
they desugar to take plain symbols only (a non-symbol binding errors, as
in Clojure).

self-hosting-compiler.md: the 'compile destructuring via a shared
destructure expander instead of falling back' item is done (and its
jolt-7dl ref was stale) — destructuring now compiles through the
fn/let/loop/defn macros' desugaring; the primitives reject patterns.

doc/grammar.ebnf

@@ -164,8 +164,11 @@ feature         = ":clj" | ":cljs" | ":default" | keyword ;
 tagged-literal  = "#" , symbol , ws , form ;
 
 (* ── Destructuring (semantics, not reader syntax) ────────────────────────────
-   The reader produces plain vectors and maps; the binding forms (let, fn, loop,
-   doseq, for, defmacro params, …) interpret them as destructuring patterns:
+   The reader produces plain vectors and maps; the binding MACROS (let, fn, loop,
+   doseq, for, defmacro params, …) interpret them as destructuring patterns. The
+   PRIMITIVES they desugar to — fn*, let*, loop* — take plain symbols ONLY (a
+   non-symbol binding is an error, as in Clojure: "fn params must be Symbols" /
+   "Bad binding form, expected symbol"). The grammar of a pattern:
 
      binding        = symbol | seq-binding | map-binding ;
      seq-binding    = "[" , { binding } , [ "&" , binding ] , [ ":as" , symbol ] , "]" ;