Make SDK ESM-only; convert VS extension to ESM (#425)

The SDK previously dual-published both ESM and CJS via tsconfig.cjs.json.
With module: Node16, tsc respected the SDK's "type": "module" and emitted
ESM syntax into dist/cjs/, which Node's CJS loader then rejected at
runtime. Production paths (CLI, MCP, VSIX bundle) all consumed the ESM
build, so the broken CJS output went unnoticed until vscode-test loaded
out/test/*.js as CJS and required the SDK transitively (#422 added the
first such SDK import to webdav-mappings.ts).

Drop the CJS build entirely and simplify the SDK exports map to ESM-only.
Convert the VS extension package to "type": "module" so its tsc test
compile emits ESM; rename the esbuild output to dist/extension.cjs (still
CJS-formatted, since VS Code requires a CJS extension entry) and point
main at the new filename. Replace two __dirname usages in tests with
fileURLToPath(import.meta.url). Re-enable the VS extension test step.

Author: clavery

.changeset/sdk-esm-only.md

@@ -0,0 +1,6 @@
+---
+'@salesforce/b2c-tooling-sdk': minor
+'b2c-vs-extension': patch
+---
+
+The SDK is now ESM-only — the dual-format `dist/cjs` build has been removed and the package exports map exposes only ESM. CommonJS consumers that previously did `require('@salesforce/b2c-tooling-sdk')` from a CJS package must either switch to `import` or rely on Node's `require(esm)` (Node ≥22.12). The VS Code extension has been converted to a `"type": "module"` package; its bundled entry is now `dist/extension.cjs`.

.github/workflows/ci-vs-extension.yml

@@ -73,11 +73,6 @@ jobs:
       - name: Build packages
         run: pnpm -r run build
 
-      # Temporarily disabled: SDK dist/cjs emits ESM syntax (tsc with module: Node16
-      # respects the SDK's "type": "module"), which Node's CJS loader rejects when
-      # vscode-test requires it transitively from out/test/*.js. The production VSIX
-      # is unaffected because esbuild bundles the SDK directly. Re-enable once the
-      # SDK CJS emit is fixed.
-      # - name: Run VS Extension tests
-      #   working-directory: packages/b2c-vs-extension
-      #   run: xvfb-run -a pnpm run test
+      - name: Run VS Extension tests
+        working-directory: packages/b2c-vs-extension
+        run: xvfb-run -a pnpm run test