destructuring compliance, deps.edn comments, clojure.java.io shim

Destructuring (drove by trying to load Selmer):
- defmacro params now destructure like fn (parse-params + destructure-bind), so
  [& [a & more :as all]] and {:keys ...} work in macro arglists.
- map-destructuring a sequential value treats it as keyword args (alternating
  k/v, or a trailing map) — the [& {:keys [...]}] form, in fns and macros.
- :keys/:syms accept namespaced symbols (x/y): looks up the namespaced key,
  binds the bare local.

deps.edn: read with Jolt's reader instead of Janet's parse, so EDN ';' line
comments are handled (Janet treats ';' as splice).

clojure.java.io: the shim was at clojure/java_io.clj (ns clojure.java-io, never
the clojure.java.io that code requires) and used bare-qualified Janet calls that
the janet.* bridge no longer resolves. Moved to clojure/java/io.clj and rewritten
on janet.file/os: file/reader/writer/resource/copy/delete-file/make-parents.

Specs in destructuring-spec; destructuring note in the ebnf.

doc/grammar.ebnf

@@ -162,3 +162,21 @@ feature         = ":clj" | ":cljs" | ":default" | keyword ;
 (* Tagged literal: #tag form. Built-in tags include #inst and #uuid; others
    dispatch to a registered data-reader (else error). *)
 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:
+
+     binding        = symbol | seq-binding | map-binding ;
+     seq-binding    = "[" , { binding } , [ "&" , binding ] , [ ":as" , symbol ] , "]" ;
+     map-binding    = "{" , { binding , form           (* {local key} *)
+                            | ":keys" , "[" {symbol} "]"   (* x or ns/x  *)
+                            | ":strs" , "[" {symbol} "]"
+                            | ":syms" , "[" {symbol} "]"
+                            | ":or"   , map                (* defaults   *)
+                            | ":as"   , symbol } , "}" ;
+
+   A symbol in :keys/:syms may be namespaced (x/y): the namespaced key is looked
+   up but the local is the bare name (y). Destructuring a *sequence* with a
+   map-binding treats it as keyword args (alternating k v, or a trailing map) —
+   this is the fn/macro `[& {:keys [...]}]` form. *)