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/jsonista.clj

@@ -1,10 +1,10 @@
-; jsonista.clj — Production JSON library example for Clojure/Nim
+; jsonista.clj — Production JSON library example for Bara Lang
 ; Modeled after https://github.com/metosin/jsonista
 ; Replaces Java/Jackson dependencies with native Nim JSON performance
 ;
 ; This example demonstrates:
 ;   - Fast JSON encoding/decoding without JVM overhead
-;   - Keyword keys support (Clojure idiomatic)
+;   - Keyword keys support (Bara Lang idiomatic)
 ;   - File I/O
 ;   - Pretty printing
 ;   - Complex nested data structures