feat: add fullscreen TUI with illwill

- New screens: Main Menu, Compile, Run, REPL, AI Generator, AI Settings, Help
- AI configuration persisted in ~/.config/cljnim/config.json
- Navigate with arrow keys, Enter, Escape
- illwill added as dependency in cljnim.nimble

src/tui_config.nim

@@ -0,0 +1,109 @@
+# TUI Configuration Manager
+# Handles persistent config in ~/.config/cljnim/config.json
+
+import std/[json, os, strutils]
+import ai_assist
+
+type
+  TuiConfig* = object
+    provider*: string      # "deepseek", "openai", "mimo", "custom"
+    model*: string
+    baseUrl*: string
+    apiKey*: string
+    timeoutMs*: int
+    lastFile*: string      # last used .clj file
+
+const
+  DefaultProviders = {
+    "deepseek": ("https://api.deepseek.com", "deepseek-chat"),
+    "openai": ("https://api.openai.com", "gpt-4o-mini"),
+    "mimo": ("https://api.mi-mo.ai", "mimo-chat"),
+    "custom": ("", "")
+  }
+
+proc configDir(): string =
+  getHomeDir() / ".config" / "cljnim"
+
+proc configPath(): string =
+  configDir() / "config.json"
+
+proc defaultConfig*(): TuiConfig =
+  result.provider = "deepseek"
+  result.model = "deepseek-chat"
+  result.baseUrl = "https://api.deepseek.com"
+  result.apiKey = ""
+  result.timeoutMs = 15000
+  result.lastFile = ""
+
+proc loadConfig*(): TuiConfig =
+  let path = configPath()
+  if not fileExists(path):
+    return defaultConfig()
+  try:
+    let jsonStr = readFile(path)
+    let j = parseJson(jsonStr)
+    result.provider = j{"provider"}.getStr("deepseek")
+    result.model = j{"model"}.getStr("deepseek-chat")
+    result.baseUrl = j{"baseUrl"}.getStr("https://api.deepseek.com")
+    result.apiKey = j{"apiKey"}.getStr("")
+    result.timeoutMs = j{"timeoutMs"}.getInt(15000)
+    result.lastFile = j{"lastFile"}.getStr("")
+  except:
+    result = defaultConfig()
+
+proc saveConfig*(cfg: TuiConfig) =
+  let dir = configDir()
+  if not dirExists(dir):
+    createDir(dir)
+  let j = %*{
+    "provider": cfg.provider,
+    "model": cfg.model,
+    "baseUrl": cfg.baseUrl,
+    "apiKey": cfg.apiKey,
+    "timeoutMs": cfg.timeoutMs,
+    "lastFile": cfg.lastFile
+  }
+  writeFile(configPath(), pretty(j))
+
+proc toAiConfig*(cfg: TuiConfig): AiConfig =
+  ## Convert TUI config to AiConfig for ai_assist module
+  result.apiKey = cfg.apiKey
+  result.baseUrl = cfg.baseUrl
+  result.model = cfg.model
+  result.timeoutMs = cfg.timeoutMs
+  if cfg.provider == "deepseek":
+    result.provider = aiDeepSeek
+  else:
+    result.provider = aiOpenAiCompatible
+
+proc fromAiConfig*(cfg: AiConfig): TuiConfig =
+  ## Convert AiConfig to TUI config
+  result.apiKey = cfg.apiKey
+  result.baseUrl = cfg.baseUrl
+  result.model = cfg.model
+  result.timeoutMs = cfg.timeoutMs
+  if cfg.provider == aiDeepSeek:
+    result.provider = "deepseek"
+  else:
+    result.provider = "openai"
+
+proc isValid*(cfg: TuiConfig): bool =
+  cfg.apiKey.len > 0 and cfg.baseUrl.len > 0 and cfg.model.len > 0
+
+proc providerDefaults*(provider: string): tuple[baseUrl, model: string] =
+  for i in 0..<DefaultProviders.len:
+    if DefaultProviders[i][0] == provider:
+      return DefaultProviders[i][1]
+  return ("", "")
+
+proc cycleProvider*(current: string, direction: int): string =
+  let providers = @["deepseek", "openai", "mimo", "custom"]
+  var idx = providers.find(current)
+  if idx < 0: idx = 0
+  idx = (idx + direction + providers.len) mod providers.len
+  return providers[idx]
+
+proc maskedKey*(cfg: TuiConfig): string =
+  if cfg.apiKey.len <= 4:
+    return ""
+  return "*".repeat(cfg.apiKey.len - 4) & cfg.apiKey[^4..^1]