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

src/ai_assist.nim

@@ -2,7 +2,7 @@
 # Supports DeepSeek API and OpenAI-compatible APIs (Xiaomi MiMo, etc.)
 # API keys are read from environment variables — never hardcoded.
 
-import std/[httpclient, json, os, strutils, uri]
+import std/[httpclient, json, os, strutils, uri, tables, times]
 
 type
   AiProvider* = enum
@@ -64,6 +64,35 @@ proc detectConfig*(): AiConfig =
 proc hasAiConfig*(): bool =
   detectConfig().apiKey.len > 0
 
+type
+  ErrorCacheEntry = object
+    suggestion: string
+    timestamp: float64
+
+var errorCache = initTable[string, ErrorCacheEntry]()
+var errorCacheMaxSize = 50
+
+proc errorCacheKey(errorMsg, fileName: string): string =
+  result = fileName & "::" & errorMsg
+  if result.len > 200:
+    result = result[0..199]
+
+proc cacheError*(errorMsg, fileName: string, suggestion: string) =
+  if errorCache.len >= errorCacheMaxSize:
+    errorCache.clear()
+  errorCache[errorCacheKey(errorMsg, fileName)] = ErrorCacheEntry(
+    suggestion: suggestion,
+    timestamp: epochTime()
+  )
+
+proc getCachedError*(errorMsg, fileName: string): string =
+  let key = errorCacheKey(errorMsg, fileName)
+  if key in errorCache:
+    let entry = errorCache[key]
+    if epochTime() - entry.timestamp < 3600.0:
+      return entry.suggestion
+  return ""
+
 proc buildErrorPrompt*(errorMsg, sourceCode, fileName: string): string =
   ## Build a prompt for the AI to analyze a compiler error
   result = """You are an expert Clojure/Nim compiler assistant. The user got a compilation error.
@@ -98,6 +127,43 @@ Requirements:
 - Return ONLY the Clojure code, no explanations
 """
 
+proc buildOptimizationPrompt*(code: string): string =
+  ## Build a prompt for AI optimization suggestions
+  result = """You are an expert Clojure performance engineer. Analyze this Clojure code and suggest optimizations:
+
+```clojure
+""" & code & """
+```
+
+Consider:
+- SIMD/vectorization opportunities
+- loop/recur vs recursion
+- Persistent data structure usage
+- Transients for batch operations
+- Parallelization opportunities (pmap, reducers)
+
+Keep response under 200 words. Return ONLY Clojure code suggestions, no explanations.
+"""
+
+proc buildDebugPrompt*(code: string, evalResult: string): string =
+  ## Build a prompt for AI debugging analysis
+  result = """You are an expert Clojure debugger. Analyze this Clojure expression and its result:
+
+**Expression:**
+```clojure
+""" & code & """
+```
+
+**Result:**
+```
+""" & evalResult & """
+```
+
+Explain what happened step by step. If there's a bug or unexpected behavior, explain why.
+Keep response under 200 words.
+Respond in the same language as the user's source code comments (Bulgarian or English).
+"""
+
 proc callAiApi*(config: AiConfig, prompt: string): AiResponse =
   ## Call the AI API and return the response
   if config.apiKey.len == 0:
@@ -139,9 +205,15 @@ proc callAiApi*(config: AiConfig, prompt: string): AiResponse =
 
 proc explainError*(errorMsg, sourceCode, fileName: string): AiResponse =
   ## High-level helper: explain a compiler error using AI
+  let cached = getCachedError(errorMsg, fileName)
+  if cached.len > 0:
+    return AiResponse(ok: true, suggestion: cached)
   let config = detectConfig()
   let prompt = buildErrorPrompt(errorMsg, sourceCode, fileName)
-  return callAiApi(config, prompt)
+  let res = callAiApi(config, prompt)
+  if res.ok:
+    cacheError(errorMsg, fileName, res.suggestion)
+  return res
 
 proc generateCode*(description: string): AiResponse =
   ## High-level helper: generate Clojure code from description
@@ -149,6 +221,18 @@ proc generateCode*(description: string): AiResponse =
   let prompt = buildGenerationPrompt(description)
   return callAiApi(config, prompt)
 
+proc optimizeCode*(code: string): AiResponse =
+  ## High-level helper: suggest optimizations for Clojure code
+  let config = detectConfig()
+  let prompt = buildOptimizationPrompt(code)
+  return callAiApi(config, prompt)
+
+proc debugCode*(code: string, evalResult: string): AiResponse =
+  ## High-level helper: debug a Clojure expression and its result
+  let config = detectConfig()
+  let prompt = buildDebugPrompt(code, evalResult)
+  return callAiApi(config, prompt)
+
 proc formatSuggestion*(response: AiResponse): string =
   ## Format AI response for terminal display
   if not response.ok: