Add bb.edn runner scripts and improve nREPL port handling

- bb.edn with compile/test/repl/nrepl/clean/fmt tasks
- nREPL checks .nrepl-port for existing server before starting
- Cleans up .nrepl-port on shutdown
- Add .nrepl-port to .gitignore

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

bb.edn

@@ -0,0 +1,27 @@
+{:tasks
+ {compile {:doc  "Compile all .clje and .ex files"
+           :task (shell "mix compile")}
+
+  test    {:doc  "Run all tests"
+           :task (shell "mix test")}
+
+  test:trace {:doc  "Run all tests with trace output"
+              :task (shell "mix test --trace")}
+
+  repl    {:doc  "Start interactive CljElixir REPL"
+           :task (shell "rlwrap mix clje.repl")}
+
+  repl:basic {:doc  "Start REPL without rlwrap"
+              :task (shell "mix clje.repl")}
+
+  nrepl   {:doc  "Start nREPL server (random port)"
+           :task (shell "mix clje.nrepl")}
+
+  nrepl:port {:doc  "Start nREPL on port 7888"
+              :task (shell "mix clje.nrepl --port 7888")}
+
+  clean   {:doc  "Clean build artifacts"
+           :task (shell "mix clean")}
+
+  fmt     {:doc  "Format Elixir source files"
+           :task (shell "mix format")}}}