feat(command): add isApplicable method to ShireCommand

Introduce a default `isApplicable` method in `ShireCommand` interface and override it in `RipgrepSearchShireCommand` to check for ripgrep binary availability.

shirelang/src/main/kotlin/com/phodal/shirelang/compiler/execute/command/RipgrepSearchShireCommand.kt

@@ -6,6 +6,10 @@ import com.phodal.shirelang.compiler.execute.command.search.RipgrepSearcher
 class RipgrepSearchShireCommand(
     val myProject: Project, private val scope: String, val text: String?,
 ) : ShireCommand {
+    override fun isApplicable(): Boolean {
+        return RipgrepSearcher.findRipgrepBinary() != null
+    }
+
     override suspend fun doExecute(): String? {
         val searchDirectory = myProject.baseDir!!.path
         return RipgrepSearcher.searchFiles(myProject, searchDirectory, text ?: scope, null).get()

shirelang/src/main/kotlin/com/phodal/shirelang/compiler/execute/command/ShireCommand.kt

@@ -1,6 +1,10 @@
 package com.phodal.shirelang.compiler.execute.command
 
 interface ShireCommand {
+    fun isApplicable(): Boolean {
+        return true
+    }
+
     suspend fun doExecute(): String?
 }