chore: rebrand Clojure/Nim → Bara Lang across codebase

- Bulk replace Clojure/Nim → Bara Lang in src/, lib/, examples/, benchmarks/,
  experiments/, books/, LICENSE, cljnim.nimble, PLAN.md, AI_AGENT.md
- Rename book chapters: 05-clojure-nim.md → 05-bara-lang.md (en + bg)
- Update all chapter index links and anchors
- Replace project-specific 'Clojure' references with 'Bara Lang' in
  experiments/, src/ai_assist.nim, src/tui_screens.nim, src/emitter.nim,
  src/reader.nim, src/types.nim, lib/cljnim_runtime*.nim
- Keep legitimate JVM Clojure/ClojureScript/Clojure CLR references intact

examples/ai_tools.clj

@@ -1,10 +1,10 @@
 ; AI-Native Tooling Demo
-; File and Git operations from Clojure
+; File and Git operations from Bara Lang
 
 (println "=== File Operations ===")
 
 ; Write a file
-(file/write "/tmp/ai_demo.txt" "Hello from Clojure/Nim AI!")
+(file/write "/tmp/ai_demo.txt" "Hello from Bara Lang AI!")
 
 ; Read it back
 (println (file/read "/tmp/ai_demo.txt"))