fix: bundle WASM dependency for Python formatting support (#426)

- Add @wasm-fmt/ruff_fmt as devDependency for build-time bundling
- Add static import hint in main.ts so ncc can detect the package
- Bundle WASM binary (ruff_fmt_bg.wasm) to dist for runtime usage
- Add Jest mock to prevent test failures with ESM-only package

This fixes the "Cannot find package '@wasm-fmt/ruff_fmt'" error that
occurred when gitstream-core 2.1.216+ tried to initialize Python formatting.

The solution works for both environments:
- GitHub Actions: WASM bundled by ncc, loaded via dynamic import
- Lambda: WASM loaded from node_modules via dynamic import

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude <noreply@anthropic.com>

Author: MishaKav

__mocks__/@wasm-fmt/ruff_fmt.js

@@ -0,0 +1,2 @@
+// Mock for @wasm-fmt/ruff_fmt (used only for ncc bundling hint)
+module.exports = {}

dist/index.js

@@ -38,7 +38,7 @@
   "license": "Apache-2.0",
   "dependencies": {
     "@actions/core": "^1.11.1",
-    "@linearb/gitstream-core": "2.1.216"
+    "@linearb/gitstream-core": "2.1.217"
   },
   "devDependencies": {
     "@jest/globals": "^30.2.0",
@@ -47,6 +47,7 @@
     "@typescript-eslint/eslint-plugin": "^8.46.3",
     "@typescript-eslint/parser": "^8.39.1",
     "@vercel/ncc": "^0.38.4",
+    "@wasm-fmt/ruff_fmt": "^0.10.0",
     "eslint": "^9.39.1",
     "eslint-plugin-github": "^5.1.8",
     "eslint-plugin-jest": "^28.13.0",
@@ -85,6 +86,9 @@
     "collectCoverage": true,
     "collectCoverageFrom": [
       "./src/**"
-    ]
+    ],
+    "moduleNameMapper": {
+      "@wasm-fmt/ruff_fmt": "<rootDir>/__mocks__/@wasm-fmt/ruff_fmt.js"
+    }
   }
 }

dist/licenses.txt

@@ -3,6 +3,9 @@ import { RulesEngine } from '@linearb/gitstream-core'
 import { version } from '@linearb/gitstream-core/package.json'
 import { installBlack } from './support-python'
 
+// Hint for ncc to bundle WASM package (used dynamically in gitstream-core)
+import '@wasm-fmt/ruff_fmt'
+
 export async function run(): Promise<void> {
   await installBlack()