Phase 4/7: nREPL, Tool-call format, Module caching

T4.5 nREPL: TCP-based JSON REPL (cljnim repl --tcp 9999)
T4.6 Tool-call: {"tool":"cljnim/eval","args":{"form":"..."}}
T7.3 Module caching: nimcache/ in project dir, skip regen if unchanged

Phase 4 now 100% complete. Phase 7: 3/4 tasks done.

src/cljnim.nim

@@ -1,5 +1,5 @@
 # Clojure/Nim — AI-First Clojure Compiler
-import os, osproc, strutils
+import os, osproc, strutils, times
 import reader, emitter, types, repl, macros
 
 proc getLibPath(): string =
@@ -113,14 +113,45 @@ proc runFile*(inputPath: string) =
   let baseName = inputPath.splitFile.name
   let nimPath = tmpDir / baseName & "_generated.nim"
   let binPath = tmpDir / baseName & "_generated"
-  
+
+  # Check nimcache for cached output
+  let projectDir = inputPath.parentDir
+  let cacheDir = projectDir / "nimcache"
+  let cacheNimPath = cacheDir / baseName & ".nim"
+  let cacheBinPath = cacheDir / baseName
+
+  var useCache = false
+  if fileExists(cacheNimPath) and fileExists(cacheBinPath):
+    let srcTime = getLastModificationTime(inputPath).toUnix
+    let cacheTime = getLastModificationTime(cacheNimPath).toUnix
+    if srcTime <= cacheTime:
+      useCache = true
+
+  if useCache:
+    echo "Using cached: ", cacheNimPath
+    let compileResult = nimCompile(cacheNimPath, cacheBinPath)
+    if compileResult != 0:
+      stderr.writeLine("Compilation failed (cached)")
+      quit(1)
+    let runResult = execCmd(cacheBinPath)
+    quit(runResult)
+
   compileFile(inputPath, nimPath)
-  
+
   let compileResult = nimCompile(nimPath, binPath)
   if compileResult != 0:
     stderr.writeLine("Compilation failed")
     quit(1)
-  
+
+  # Save to cache
+  try:
+    createDir(cacheDir)
+    copyFile(nimPath, cacheNimPath)
+    copyFile(binPath, cacheBinPath)
+    echo "Cached: ", cacheNimPath
+  except:
+    discard
+
   let runResult = execCmd(binPath)
   if runResult != 0:
     stderr.writeLine("Execution failed")
@@ -199,17 +230,34 @@ proc main() =
   
   of "repl":
     var mode = rmHuman
+    var tcpPort = -1
     for i in 1..<args.len:
       if args[i] == "--json":
         mode = rmJson
       elif args[i] == "--edn":
         mode = rmEdn
+      elif args[i] == "--tcp":
+        if i + 1 < args.len:
+          try:
+            tcpPort = parseInt(args[i+1])
+          except ValueError:
+            stderr.writeLine("Invalid TCP port: " & args[i+1])
+            quit(1)
+      elif args[i].startsWith("--tcp="):
+        try:
+          tcpPort = parseInt(args[i][6..^1])
+        except ValueError:
+          stderr.writeLine("Invalid TCP port: " & args[i][6..^1])
+          quit(1)
     var state = initReplState(mode)
     try:
-      case mode
-      of rmHuman: runHumanRepl(state)
-      of rmJson: runJsonRepl(state)
-      of rmEdn: runJsonRepl(state)
+      if tcpPort > 0:
+        runTcpRepl(state, tcpPort)
+      else:
+        case mode
+        of rmHuman: runHumanRepl(state)
+        of rmJson: runJsonRepl(state)
+        of rmEdn: runJsonRepl(state)
     finally:
       state.cleanup()