test(sequencer-client): fix checkpoint proposal job timetable setup

[AztecBot]

Summary

• Ensure fresh jobs created in the single-block checkpoint proposal tests use the same one-block timetable as the describe setup.
• Make the pipelined parent helper explicitly use that one-block timetable and start at the pipelined build-frame opening.

Investigation

PR #24331 was dequeued after the merge-queue run for synthetic commit 08e8db39e998b8a5ad95b09039de2befd48e144f failed ci/x3-full. The failed test log for yarn-project/scripts/run_test.sh sequencer-client/src/sequencer/checkpoint_proposal_job.test.ts showed TypeError: Cannot read properties of undefined (reading 'getStats') at block.getStats() in checkpoint_proposal_job.ts.

The test helpers seeded a single mock block, but some freshly-created pipelined jobs kept the default multi-block timetable instead of the single-block timetable. With no-op waits in the test subclass, the job attempted a second block build, exhausted MockCheckpointBuilder, and returned an undefined block.

Verification

• MAKEFILE_TARGET=yarn-project yarn-project/scripts/run_test.sh sequencer-client/src/sequencer/checkpoint_proposal_job.test.ts (46 passed)
• ./bootstrap.sh ci exits immediately with Unknown command: ci on this branch; the root bootstrap defines ci-fast/ci-full, not plain ci.

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Created by claudebox · group: slackbot