Add Go v2 checkpoint migration tool

[pfleidi]

What

Adds a Go-based migration binary under cmd/migrate-v2-checkpoints to restore useful v2-only checkpoint data into v1 storage. It reuses the existing checkpoint stores instead of line-for-line porting the shell script.

How

• Adds optional commit timestamp support to committed checkpoint writes.
• Discovers checkpoint trailers in branch history after a selected base commit.
• Reads v2 metadata and raw transcript content through the v2 store.
• Writes restored v1 checkpoints through the production v1 GitStore path.
• Supports list, dry-run, and apply modes with skipped-data reporting.
• Adds focused tests for timestamp preservation, discovery, migration, dry-run, existing v1 data, and incomplete v2 data.

Notes

The migration intentionally skips transcript data that lacks usable v2 metadata, since that data is not useful for v1 restoration by itself.

Verification

• mise run lint
• go build -ldflags "-X github.com/entireio/cli/cmd/entire/cli/versioninfo.Version=v0.0.0-dev-9df43932c -X github.com/entireio/cli/cmd/entire/cli/versioninfo.Commit=9df43932c" -o /private/tmp/entire-pr-check ./cmd/entire
• go build -o /private/tmp/migrate-v2-checkpoints-pr-check ./cmd/migrate-v2-checkpoints
• go test ./cmd/entire/cli/checkpoint ./cmd/migrate-v2-checkpoints -count=1

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Note

Medium Risk
Apply mode rewrites the v1 metadata branch from discovered v2 data; mistakes could affect checkpoint history, though dry-run and skip-existing-session behavior limit exposure.

Overview
Adds a migrate-v2-checkpoints CLI that discovers checkpoints from Entire-Checkpoint trailers in normal branch history (with --since, --head, list / dry-run / apply) and restores eligible v2 sessions into v1 via the existing GitStore / V2GitStore paths, skipping sessions already on v1 and reporting missing v2 metadata or raw transcripts.

Committed checkpoint writes gain optional CommitTime so metadata-branch commits can keep historical author/committer times during migration (zero still means “now”; CreatedAt is not reused as the git timestamp). Checkpoint pushes now use an explicit refs/heads/…:refs/heads/… refspec so stale refs/entire/checkpoints/v1 refs cannot make the source branch ambiguous.

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[Copilot]

Pull request overview

Adds a standalone Go migration binary (cmd/migrate-v2-checkpoints) that discovers Entire-Checkpoint trailers in git history and restores v2-only checkpoint/session data back into the production v1 checkpoint store, including preserving historical commit timestamps when writing to the v1 metadata branch.

Changes:

• Introduces migrate-v2-checkpoints with list/plan/dry-run/apply modes, repo opening, checkpoint discovery, and migration reporting.
• Implements checkpoint discovery by scanning git history tips for Entire-Checkpoint trailers and associating checkpoint IDs with commits.
• Extends v1 committed checkpoint writes with optional CommitTime, wiring it through commit creation and adding focused tests.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
cmd/migrate-v2-checkpoints/main.go	Adds CLI entrypoint, flag parsing, repo opening, and mode dispatch for migration.
cmd/migrate-v2-checkpoints/history.go	Implements checkpoint trailer discovery by scanning reachable commits from selected history tips.
cmd/migrate-v2-checkpoints/migration.go	Implements v2→v1 migration logic and prints a summary report.
cmd/migrate-v2-checkpoints/main_test.go	Adds end-to-end tests for discovery, dry-run, apply, idempotency, and missing-data handling.
cmd/entire/cli/checkpoint/checkpoint.go	Extends WriteCommittedOptions with CommitTime.
cmd/entire/cli/checkpoint/committed.go	Uses CommitTime (or now) when creating metadata-branch commits; factors commit creation into a helper.
cmd/entire/cli/checkpoint/temporary.go	Routes commit creation through the new commit-time-aware helper.
cmd/entire/cli/checkpoint/committed_commit_time_test.go	Adds tests validating commit timestamp preservation vs “use current time” behavior.

[pfleidi]

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[Copilot]

Pull request overview

Copilot reviewed 12 out of 12 changed files in this pull request and generated 4 comments.

[pfleidi]

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