fix(ci): transform ESM @docmost/prosemirror-markdown in server int/e2e jest

The develop build failed in two jobs, both rooted in the ESM-only workspace
package @docmost/prosemirror-markdown (type: module, built to build/index.js
with `export * from`), which the server imports at runtime (collaboration.util,
page.service). Refactor #345 taught only the unit jest config (package.json
"jest" key) to consume it, leaving the integration and e2e configs — and the
e2e-server CI job — broken:

- `pnpm --filter server test:int` -> SyntaxError: Unexpected token 'export'
  (jest did not transform prosemirror-markdown/build/*.js).
- e2e-server job -> TS2307 Cannot find module '@docmost/prosemirror-markdown'
  (the package was never built in that job).

Mirror the proven unit config into the two failing jest configs and add the
missing build step:

- jest-integration.json / jest-e2e.json: add a babel-jest transform rule for
  `prosemirror-markdown/build/.+\.js$` (before the ts-jest rule so it wins) and
  add @docmost/prosemirror-markdown to the transformIgnorePatterns allowlist so
  the pnpm-symlinked package is transformed instead of ignored.
- develop.yml: build @docmost/prosemirror-markdown in the e2e-server job (after
  editor-ext, before migrations), like the test.yml job already does.

Verified locally: an isolated spec importing the package fails with the exact
SyntaxError under the old config and passes under the new one.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.github/workflows/develop.yml

@@ -151,6 +151,12 @@ jobs:
       - name: Build editor-ext
         run: pnpm --filter @docmost/editor-ext build
 
+      # @docmost/prosemirror-markdown is an ESM workspace package the server
+      # imports at runtime; its build/ is gitignored and test:e2e has no pretest
+      # hook, so build it before the e2e run (mirrors the test.yml job).
+      - name: Build prosemirror-markdown
+        run: pnpm --filter @docmost/prosemirror-markdown build
+
       - name: Run migrations
         run: pnpm --filter ./apps/server migration:latest