feat: add fullscreen TUI and project updates

- New TUI screens: Main Menu, Compile, Run, REPL, AI Generator, AI Settings, Help
- AI configuration persisted in ~/.config/cljnim/config.json
- Added illwill dependency for terminal UI
- Updated experiments, examples, docs, and core modules

tests/test_ai_assist.nim

@@ -1,15 +1,12 @@
 # Tests for AI assistance module (no real API calls)
 
-import unittest, strutils
+import unittest, strutils, times
 import os
 import ai_assist
 
 suite "AI Config Detection":
   test "detectConfig returns empty when no env vars set":
-    # Note: this test assumes no API keys are set in test environment
-    # If keys ARE set, it will detect them
     let cfg = detectConfig()
-    # At minimum, the function should not crash
     check cfg.timeoutMs >= 0
 
   test "hasAiConfig returns false when no keys set (if env empty)":
@@ -31,6 +28,30 @@ suite "Prompt Building":
     check "reverse a list" in prompt
     check "Clojure" in prompt
 
+  test "buildOptimizationPrompt includes code":
+    let prompt = buildOptimizationPrompt("(reduce + [1 2 3])")
+    check "(reduce + [1 2 3])" in prompt
+    check "SIMD" in prompt or "optim" in prompt.toLowerAscii()
+
+  test "buildDebugPrompt includes code and result":
+    let prompt = buildDebugPrompt("(+ 1 2)", "3")
+    check "(+ 1 2)" in prompt
+    check "3" in prompt
+    check "Clojure" in prompt
+
+suite "Error Cache":
+  test "getCachedError returns empty for unknown errors":
+    check getCachedError("unknown error", "test.clj") == ""
+
+  test "cacheError and getCachedError work":
+    cacheError("type mismatch", "test.clj", "Check your types")
+    check getCachedError("type mismatch", "test.clj") == "Check your types"
+
+  test "cacheError with same key returns correct suggestion":
+    cacheError("unterminated string", "src.clj", "Add closing quote")
+    let cached = getCachedError("unterminated string", "src.clj")
+    check cached == "Add closing quote"
+
 suite "Response Formatting":
   test "formatSuggestion shows error when not ok":
     let resp = AiResponse(ok: false, suggestion: "No key configured")