(Do not merge) One-time migration script for v2 checkpoints to v1

[computermode]

Example command:

To see all the checkpoints to migrate:

./scripts/migrate-v2-checkpoints-to-v1.sh \
  --repo path/to/repo \
  --since <commit sha> --list

To go through a dry run:

./scripts/migrate-v2-checkpoints-to-v1.sh \
  --repo path/to/repo \
  --since <commit sha> --dry-run

To create the commit that copies the checkpoints from v2 to v1:

./scripts/migrate-v2-checkpoints-to-v1.sh \
  --repo path/to/repo \
  --since <commit sha> --apply

To validate:
git show --stat refs/heads/entire/checkpoints/v1

To push after:
git push origin refs/heads/entire/checkpoints/v1:refs/heads/entire/checkpoints/v1

---

Note

Medium Risk
Adds a one-off migration script that can create and update the refs/heads/entire/checkpoints/v1 ref based on parsed commit trailers and checkpoint refs; misuse could write incorrect history or overwrite the local ref.

Overview
Introduces scripts/migrate-v2-checkpoints-to-v1.sh, a standalone tool to plan or apply migration of legacy v2 checkpoint artifacts back into the v1 checkpoint tree.

The script scans commits after a given --since (optionally constrained by --head) for Entire-Checkpoint trailers, maps those checkpoint IDs to v2 data under refs/entire/checkpoints/v2/full/* (raw transcripts + hashes), and pulls companion session/prompt metadata from refs/entire/checkpoints/v2/main when available.

It supports --list (checkpoint IDs + commit IDs), --dry-run (print every source artifact), and --apply, which builds a new v1 tree, rewrites checkpoint-level metadata.json to include discovered sessions, and writes a single migration commit updating refs/heads/entire/checkpoints/v1.

^{Reviewed by Cursor Bugbot for commit 1ea7f14. Configure here.}

[Copilot]

Pull request overview

Adds a standalone, one-time Bash script to migrate legacy v2 checkpoint artifacts (raw transcripts + companion metadata) into the v1 checkpoint tree and optionally write a single migration commit updating refs/heads/entire/checkpoints/v1.

Changes:

• Introduces scripts/migrate-v2-checkpoints-to-v1.sh with modes to list, dry-run, or apply a migration.
• Scans git history for Entire-Checkpoint: <12-hex> trailers and maps them to v2 full/* and main ref artifacts.
• (On --apply) rewrites checkpoint-level metadata.json to include discovered session entries and writes a migration commit.

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^{Reviewed by Cursor Bugbot for commit 1ea7f14. Configure here.}