fix(docs): repair spartan train docs CI

[AztecBot]

Summary

Fixes the docs CI failures that dequeued #23971 from the merge queue.

Investigation:

• feat: merge-train/spartan #23971 was removed from the merge queue at 2026-06-12 17:32 UTC after CI3 merge-group run 27431785060 failed in job ci; the failed leg was x5-full (http://ci.aztec-labs.com/f3fe34c749830959).
• The merge-group job runs on gh-readonly-queue/next/... with PR_BASE_REF empty and TARGET_BRANCH=next. docs/bootstrap.sh check_orphaned_urls needed the base branch snapshot, but the shallow checkout did not have origin/next available.
• The webapp tutorial build also needed current train API/dependency fixes when built as a standalone app against local linked packages.

Changes:

• Teach docs/bootstrap.sh to resolve merge-group base refs from TARGET_BRANCH, strip refs/heads/, and explicitly fetch refs/heads/<base>:refs/remotes/origin/<base> for shallow CI checkouts.
• Expand webapp tutorial local @aztec/* linking to include linked package runtime dependencies, because Yarn link: does not install dependencies from linked package manifests.
• Update the webapp tutorial PXE/fee-options code for the current wallet SDK API.

Testing

• bash -n docs/bootstrap.sh docs/examples/bootstrap.sh
• git diff --check
• CI=1 AZTEC_CACHE_COMMIT=origin/merge-train/spartan GITHUB_REF_NAME='gh-readonly-queue/next/pr-23971-deadbeef' TARGET_BRANCH=next docs/bootstrap.sh check_orphaned_urls
• docs/examples/bootstrap.sh validate-webapp-tutorial

Attempted the requested root command:

• ./bootstrap.sh ci exits with Unknown command: ci on this ref after the expected local Docker/cache warning; the root bootstrap has ci-fast, ci-full, and ci-full-no-test-cache, but no ci case.

Not fully run locally:

• Full Docker-backed docs example execution, because this session has no Docker socket (/var/run/docker.sock).

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Created by claudebox · group: slackbot