refactor(app): remove unused ViteBabelState and extract plugin name constant

- Remove ViteBabelState type definition from component-tagger.ts as it was never accessed
- Extract "component-path-babel-tagger" string to babelPluginName constant in component-path.ts
- Replace all hardcoded plugin name strings across babel-plugin.ts, component-tagger.ts, and babel.cjs
- Maintain mathematical purity: ∀p ∈ PluginName: p = babelPluginName (single source of truth)

INVARIANT: Plugin name remains stable across all implementations via shared constant
THEOREM: ∀ implementation: plugin.name = babelPluginName
QUOTE(ТЗ): "Вынести строки имён плагинов в константы (чтобы не дублировать \"component-path-babel-tagger\")."
REF: #19

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: konard

packages/app/babel.cjs

@@ -22,6 +22,7 @@
 
 const path = require("node:path")
 
+const babelPluginName = "component-path-babel-tagger"
 const componentPathAttributeName = "path"
 const jsxFilePattern = /\.(tsx|jsx)(\?.*)?$/u
 
@@ -37,7 +38,7 @@ const attrExists = (node, attrName, t) =>
 
 module.exports = function componentTaggerBabelPlugin({ types: t }) {
   return {
-    name: "component-path-babel-tagger",
+    name: babelPluginName,
     visitor: {
       JSXOpeningElement(nodePath, state) {
         const { node } = nodePath

packages/app/src/core/component-path.ts

@@ -1,5 +1,17 @@
 const jsxFilePattern = /\.(tsx|jsx)(\?.*)?$/u
 
+// CHANGE: define canonical Babel plugin name for component path tagging.
+// WHY: eliminate magic string duplication across plugin implementations.
+// QUOTE(ТЗ): "Вынести строки имён плагинов в константы (чтобы не дублировать \"component-path-babel-tagger\")."
+// REF: issue-19
+// SOURCE: n/a
+// FORMAT THEOREM: forall p in PluginName: p = "component-path-babel-tagger"
+// PURITY: CORE
+// EFFECT: n/a
+// INVARIANT: plugin name remains stable across all implementations
+// COMPLEXITY: O(1)/O(1)
+export const babelPluginName = "component-path-babel-tagger"
+
 // CHANGE: define canonical attribute name for component path tagging.
 // WHY: reduce metadata to a single attribute while keeping full source location.
 // QUOTE(TZ): "\u0421\u0430\u043c \u043a\u043e\u043c\u043f\u043e\u043d\u0435\u043d\u0442 \u0434\u043e\u043b\u0436\u0435\u043d \u0431\u044b\u0442\u044c \u0432 \u0442\u0435\u043a\u0443\u0449\u0435\u043c app \u043d\u043e \u0432\u043e\u0442 \u0447\u0442\u043e \u0431\u044b \u0435\u0433\u043e \u043f\u0440\u043e\u0442\u0435\u0441\u0442\u0438\u0440\u043e\u0432\u0430\u0442\u044c \u043d\u0430\u0434\u043e \u0441\u043e\u0437\u0434\u0430\u0442\u044c \u0435\u0449\u0451 \u043e\u0434\u0438\u043d \u043f\u0440\u043e\u0435\u043a\u0442 \u043a\u043e\u0442\u043e\u0440\u044b\u0439 \u043d\u0430\u0448 \u0442\u0435\u043a\u0443\u0449\u0438\u0439 \u0430\u043f\u043f \u0431\u0443\u0434\u0435\u0442 \u043f\u043e\u0434\u043a\u043b\u044e\u0447\u0430\u0442\u044c"

packages/app/src/shell/babel-plugin.ts

@@ -1,6 +1,6 @@
 import { type PluginObj, types as t } from "@babel/core"
 
-import { isJsxFile } from "../core/component-path.js"
+import { babelPluginName, isJsxFile } from "../core/component-path.js"
 import { createJsxTaggerVisitor, type JsxTaggerContext } from "../core/jsx-tagger.js"
 import { computeRelativePath } from "../core/path-service.js"
 
@@ -106,7 +106,7 @@ const getContextFromState = (state: BabelState): JsxTaggerContext | null => {
 // INVARIANT: each JSX opening element has at most one path attribute
 // COMPLEXITY: O(n)/O(1)
 export const componentTaggerBabelPlugin = (): PluginObj<BabelState> => ({
-  name: "component-path-babel-tagger",
+  name: babelPluginName,
   visitor: createJsxTaggerVisitor<BabelState>(getContextFromState, t)
 })
 

packages/app/src/shell/component-tagger.ts

@@ -3,7 +3,7 @@ import type { Path } from "@effect/platform/Path"
 import { Effect, pipe } from "effect"
 import type { PluginOption } from "vite"
 
-import { isJsxFile } from "../core/component-path.js"
+import { babelPluginName, isJsxFile } from "../core/component-path.js"
 import { createJsxTaggerVisitor, type JsxTaggerContext } from "../core/jsx-tagger.js"
 import { NodePathLayer, relativeFromRoot } from "../core/path-service.js"
 
@@ -50,16 +50,12 @@ const toViteResult = (result: BabelTransformResult): ViteTransformResult | null
 // EFFECT: Babel AST transformation
 // INVARIANT: each JSX opening element has at most one path attribute
 // COMPLEXITY: O(n)/O(1), n = number of JSX elements
-type ViteBabelState = {
-  readonly context: JsxTaggerContext
-}
-
-const makeBabelTagger = (relativeFilename: string): PluginObj<ViteBabelState> => {
+const makeBabelTagger = (relativeFilename: string): PluginObj => {
   const context: JsxTaggerContext = { relativeFilename }
 
   return {
-    name: "component-path-babel-tagger",
-    visitor: createJsxTaggerVisitor<ViteBabelState>(
+    name: babelPluginName,
+    visitor: createJsxTaggerVisitor(
       () => context,
       t
     )