Add Vortex extension scaffold + MCP stdio client (Unit E)

vortex-extension/.editorconfig

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+# This folder is a separate, idiomatic Node/TypeScript project (see README.md), not part
+# of the .NET solution. LF line endings are the standard convention for that ecosystem -
+# and what npm itself always writes for generated files like package-lock.json - so this
+# scopes an override of the repo root .editorconfig's `end_of_line = crlf` (a convention
+# for the .cs/.NET side, see CONTRIBUTING.md) to everything under this folder, rather than
+# changing the shared root file.
+[*]
+end_of_line = lf

vortex-extension/.gitattributes

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+# Force LF for this folder's text files regardless of a contributor's local git
+# core.autocrlf setting - the standard, idiomatic convention for a Node/TypeScript
+# package (see .editorconfig and README.md), independent of the repo root's CRLF
+# convention for the .NET/.cs side (see CONTRIBUTING.md).
+* text=auto eol=lf

vortex-extension/.gitignore

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+node_modules/
+dist/
+*.tsbuildinfo
+coverage/

vortex-extension/README.md

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+# witcherscriptmerger-vortex
+
+A [Vortex](https://www.nexusmods.com/about/vortex/) (Nexus Mods' mod manager) companion
+extension for WitcherScriptMerger (WSM). It drives WSM's `mcp` server mode (see the repo
+root `CLAUDE.md` and `WitcherScriptMerger.Core/Mcp/CLAUDE.md`) from inside Vortex, as a
+companion to Vortex's own built-in `game-witcher3` extension - it does **not** register
+the `witcher3` game itself, and every feature it adds is gated on Witcher 3 being the
+currently active game.
+
+## This is a separate toolchain
+
+Everything under this folder is TypeScript/Node, built with its own `package.json`,
+independent of the rest of this repository's .NET solution
+(`WitcherScriptMerger.sln`). `dotnet build`/`dotnet format` at the repo root never look
+inside this folder, and nothing here is reachable from them.
+
+```
+cd vortex-extension
+npm install
+npm run build      # typecheck + webpack bundle -> dist/index.js
+npm run lint
+npm test           # fast, Node-only unit tests
+```
+
+`npm test` only runs the fast, Node-only unit tests (`src/**/*.test.ts`) - no .NET SDK
+needed. `src/mcpClient.ts`'s real, spawned-process integration test
+(`test/mcpClient.integration.test.ts`) is a separate script, `npm run test:integration`,
+since it needs a local .NET SDK and a buildable `WitcherScriptMerger.Headless` (it will
+run `dotnet build` itself if the exe isn't already present) - kept out of the default
+`npm test` so a Node-only environment (e.g. a contributor machine or CI runner without
+the .NET SDK on `PATH`) isn't forced through a multi-minute .NET build just to iterate on
+this extension's own TypeScript.
+
+## Status
+
+This is the foundation scaffold (info.json manifest, build tooling, the `init(context)`
+entry point with only game-activity gating wired up, and the shared MCP stdio client in
+`src/mcpClient.ts`). No actual features - tool acquisition, conflict scanning, the merge
+panel, dashlets - are implemented here; those are separate, later units built on top of
+this scaffold. See `docs/vortex-extension-design.md` (once merged) for the fuller design
+context this scaffold follows.

vortex-extension/eslint.config.mjs

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+// Flat ESLint config (ESLint 9+). Basic, sane TypeScript linting - not the type-checked
+// preset (`recommendedTypeChecked`), to keep this fast and dependency-light for a v1
+// scaffold; a later unit can upgrade to type-aware rules if that becomes worthwhile.
+import tseslint from 'typescript-eslint';
+
+export default tseslint.config(
+  {
+    ignores: ['dist/**', 'node_modules/**'],
+  },
+  ...tseslint.configs.recommended,
+  {
+    rules: {
+      '@typescript-eslint/no-unused-vars': ['warn', { argsIgnorePattern: '^_' }],
+    },
+  },
+);

vortex-extension/info.json

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+{
+  "name": "WitcherScriptMerger Companion",
+  "author": "TheValiantOne/WitcherScriptMerger contributors",
+  "version": "0.1.0",
+  "description": "Companion Vortex extension for WitcherScriptMerger (WSM) - drives WSM's MCP server for Witcher 3 script-conflict scanning and merging from inside Vortex."
+}