feat: undo session file mutations via server endpoint + CLI command

apps/cli/src/main/kotlin/com/correx/apps/cli/CorrexCli.kt

@@ -5,6 +5,7 @@ import com.correx.apps.cli.commands.ProviderCommand
 import com.correx.apps.cli.commands.RunCommand
 import com.correx.apps.cli.commands.SessionCommand
 import com.correx.apps.cli.commands.StatusCommand
+import com.correx.apps.cli.commands.UndoCommand
 import com.github.ajalt.clikt.core.CliktCommand
 import com.github.ajalt.clikt.core.subcommands
 import com.github.ajalt.clikt.parameters.options.flag
@@ -23,4 +24,5 @@ fun buildCli(): CorrexCli = CorrexCli().subcommands(
     ApproveCommand(),
     StatusCommand(),
     ProviderCommand(),
+    UndoCommand(),
 )

apps/cli/src/main/kotlin/com/correx/apps/cli/commands/UndoCommand.kt

@@ -0,0 +1,29 @@
+package com.correx.apps.cli.commands
+
+import com.correx.apps.cli.DEFAULT_PORT
+import com.github.ajalt.clikt.core.CliktCommand
+import com.github.ajalt.clikt.parameters.arguments.argument
+import com.github.ajalt.clikt.parameters.options.default
+import com.github.ajalt.clikt.parameters.options.option
+import io.ktor.client.HttpClient
+import io.ktor.client.engine.cio.CIO
+import io.ktor.client.request.post
+import io.ktor.client.statement.bodyAsText
+import kotlinx.coroutines.runBlocking
+
+class UndoCommand : CliktCommand(name = "undo") {
+    private val sessionId by argument("SESSION_ID")
+    private val host by option("--host").default("localhost")
+    private val port by option("--port").default("$DEFAULT_PORT")
+
+    override fun run(): Unit = runBlocking {
+        val portInt = port.toIntOrNull() ?: DEFAULT_PORT
+        val client = HttpClient(CIO)
+        try {
+            val response = client.post("http://$host:$portInt/sessions/$sessionId/undo")
+            echo(response.bodyAsText())
+        } finally {
+            client.close()
+        }
+    }
+}