Phase 8: REPL, printing, source maps, and nREPL server

- IPrintWithWriter protocol + CljElixir.Printer module with pr-str,
  print-str, pr, prn for all BEAM types (EDN-like output)
- Source-mapped error messages: line/col metadata from reader now
  propagated through transformer into Elixir AST for accurate error
  locations in .clje files
- Interactive REPL (mix clje.repl) with multi-line input detection,
  history, bindings persistence, and pr-str formatted output
- nREPL server (mix clje.nrepl) with TCP transport, Bencode wire
  protocol, session management, and core operations (clone, close,
  eval, describe, ls-sessions, load-file, interrupt, completions).
  Writes .nrepl-port for editor auto-discovery.

92 new tests (699 total, 0 failures).

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

test/clj_elixir/transformer_test.exs

@@ -1079,12 +1079,12 @@ defmodule CljElixir.TransformerTest do
   describe "dynamic vars" do
     test "*self* produces self() call" do
       ast = transform("*self*")
-      assert ast == {:self, [], []}
+      assert match?({:self, _, []}, ast)
     end
 
     test "*node* produces node() call" do
       ast = transform("*node*")
-      assert ast == {:node, [], []}
+      assert match?({:node, _, []}, ast)
     end
 
     test "*self* evaluates to current process" do
@@ -1131,12 +1131,12 @@ defmodule CljElixir.TransformerTest do
   describe "symbols" do
     test "plain symbol becomes variable" do
       ast = transform("x")
-      assert ast == {:x, [], nil}
+      assert match?({:x, _, nil}, ast)
     end
 
     test "symbol with hyphens becomes munged variable" do
       ast = transform("my-var")
-      assert ast == {:my_var, [], nil}
+      assert match?({:my_var, _, nil}, ast)
     end
 
     test "true symbol becomes true literal" do