fix(docs): repair merge queue docs checks

[AztecBot]

Summary

Investigated the latest merge-train/spartan dequeue for PR #23971. The PR is still mergeable against next; the latest removal from the merge queue happened at 2026-06-15T10:50:03Z after the synthetic merge-group SHA f202a73a3147bc7a5342b73ea4298f95040e762b failed CI.

The failing docs subjob ended with:

ERROR: cannot resolve base branch origin/next to source the orphan-check baseline.

That happens because merge-group checkouts may not have origin/next locally. The same subjob also showed real Vite resolution failures for local linked tutorial packages, but the docs examples wrapper masked them by disabling errexit while capturing step output.

Changes

• Fetch the orphan URL baseline branch explicitly into refs/remotes/origin/<base> when it is missing, and honor MERGE_GROUP_BASE_REF for merge-group events.
• Add @aztec/protocol-contracts to the webapp tutorial dependency list.
• Make webapp tutorial CI linking add the local @aztec/* dependency closure for workspace:, portal:, and file: deps, so local link: installs behave like published npm package installs for transitive workspace packages such as @aztec/blob-lib and @aztec/bb.js.
• Copy normal npm dependencies from linked local package manifests into the temporary tutorial install, covering external transitive deps such as lodash.times.
• Keep errexit enabled inside docs example step capture so failing commands such as npx vite build are reported instead of followed by a success line.

Verification

• bash -n docs/bootstrap.sh docs/examples/bootstrap.sh
• CI=1 GITHUB_EVENT_NAME=merge_group MERGE_GROUP_BASE_REF=refs/heads/next docs/bootstrap.sh check_orphaned_urls
• Bounded webapp tutorial Yarn link/install check with corepack yarn@4.13.0 install --mode=skip-build, confirming @aztec/protocol-contracts, @aztec/blob-lib, @aztec/bb.js, and lodash.times resolve from the tutorial install.

Note: I also ran the exact requested ./bootstrap.sh ci; on this branch it exits immediately with Unknown command: ci, so there is no generic root ci entrypoint to run locally here.