feat: AI-assisted compilation and code generation

- New src/ai_assist.nim module with DeepSeek/OpenAI/MiMo API support
- AI explains compiler errors automatically when compilation fails
- New CLI command: cljnim ai '<description>' for code generation
- REPL :ai command for interactive AI assistance
- API keys read from environment vars (DEEPSEEK_API_KEY, OPENAI_API_KEY, MIMO_API_KEY)
- Tests for prompt building and response formatting
- Updated README with AI integration docs

tests/test_ai_assist.nim

@@ -0,0 +1,45 @@
+# Tests for AI assistance module (no real API calls)
+
+import unittest, strutils
+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)":
+    let key = getEnv("DEEPSEEK_API_KEY", "")
+    let okey = getEnv("OPENAI_API_KEY", "")
+    let mkey = getEnv("MIMO_API_KEY", "")
+    if key.len == 0 and okey.len == 0 and mkey.len == 0:
+      check hasAiConfig() == false
+
+suite "Prompt Building":
+  test "buildErrorPrompt includes filename and source":
+    let prompt = buildErrorPrompt("type mismatch", "(defn foo [x] x)", "test.clj")
+    check "test.clj" in prompt
+    check "type mismatch" in prompt
+    check "(defn foo [x] x)" in prompt
+
+  test "buildGenerationPrompt includes description":
+    let prompt = buildGenerationPrompt("reverse a list")
+    check "reverse a list" in prompt
+    check "Clojure" in prompt
+
+suite "Response Formatting":
+  test "formatSuggestion shows error when not ok":
+    let resp = AiResponse(ok: false, suggestion: "No key configured")
+    let formatted = formatSuggestion(resp)
+    check "💡 AI:" in formatted
+    check "No key configured" in formatted
+
+  test "formatSuggestion shows suggestion when ok":
+    let resp = AiResponse(ok: true, suggestion: "Use (reverse coll)")
+    let formatted = formatSuggestion(resp)
+    check "💡 AI Suggestion:" in formatted
+    check "Use (reverse coll)" in formatted